Add vacuum_freeze_table_age GUC option, to control when VACUUM should

[PostgreSQL.git] / src / backend / utils / misc / guc.c

/*--------------------------------------------------------------------
 * guc.c
 *
 * Support for grand unified configuration scheme, including SET
 * command, configuration file, and command line options.
 * See src/backend/utils/misc/README for more information.
 *
 *
 * Copyright (c) 2000-2009, PostgreSQL Global Development Group
 * Written by Peter Eisentraut <peter_e@gmx.net>.
 *
 * IDENTIFICATION
 *        $PostgreSQL$
 *
 *--------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <float.h>
#include <math.h>
#include <limits.h>
#include <unistd.h>
#include <sys/stat.h>
#ifdef HAVE_SYSLOG
#include <syslog.h>
#endif

#include "access/gin.h"
#include "access/transam.h"
#include "access/twophase.h"
#include "access/xact.h"
#include "catalog/namespace.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "commands/vacuum.h"
#include "commands/variable.h"
#include "commands/trigger.h"
#include "funcapi.h"
#include "libpq/auth.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "parser/gramparse.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "parser/scansup.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgwriter.h"
#include "postmaster/postmaster.h"
#include "postmaster/syslogger.h"
#include "postmaster/walwriter.h"
#include "regex/regex.h"
#include "storage/bufmgr.h"
#include "storage/fd.h"
#include "tcop/tcopprot.h"
#include "tsearch/ts_cache.h"
#include "utils/builtins.h"
#include "utils/guc_tables.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
#include "utils/plancache.h"
#include "utils/portal.h"
#include "utils/ps_status.h"
#include "utils/tzparser.h"
#include "utils/xml.h"

#ifndef PG_KRB_SRVTAB
#define PG_KRB_SRVTAB ""
#endif
#ifndef PG_KRB_SRVNAM
#define PG_KRB_SRVNAM ""
#endif

#define CONFIG_FILENAME "postgresql.conf"
#define HBA_FILENAME    "pg_hba.conf"
#define IDENT_FILENAME  "pg_ident.conf"

#ifdef EXEC_BACKEND
#define CONFIG_EXEC_PARAMS "global/config_exec_params"
#define CONFIG_EXEC_PARAMS_NEW "global/config_exec_params.new"
#endif

/* upper limit for GUC variables measured in kilobytes of memory */
#if SIZEOF_SIZE_T > 4
#define MAX_KILOBYTES   INT_MAX
#else
#define MAX_KILOBYTES   (INT_MAX / 1024)
#endif

#define KB_PER_MB (1024)
#define KB_PER_GB (1024*1024)

#define MS_PER_S 1000
#define S_PER_MIN 60
#define MS_PER_MIN (1000 * 60)
#define MIN_PER_H 60
#define S_PER_H (60 * 60)
#define MS_PER_H (1000 * 60 * 60)
#define MIN_PER_D (60 * 24)
#define S_PER_D (60 * 60 * 24)
#define MS_PER_D (1000 * 60 * 60 * 24)

/* XXX these should appear in other modules' header files */
extern bool Log_disconnections;
extern int      CommitDelay;
extern int      CommitSiblings;
extern char *default_tablespace;
extern char *temp_tablespaces;
extern bool synchronize_seqscans;
extern bool fullPageWrites;

#ifdef TRACE_SORT
extern bool trace_sort;
#endif
#ifdef TRACE_SYNCSCAN
extern bool trace_syncscan;
#endif
#ifdef DEBUG_BOUNDED_SORT
extern bool optimize_bounded_sort;
#endif

#ifdef USE_SSL
extern char *SSLCipherSuites;
#endif

static void set_config_sourcefile(const char *name, char *sourcefile,
                                          int sourceline);

static const char *assign_log_destination(const char *value,
                                           bool doit, GucSource source);

#ifdef HAVE_SYSLOG
static int      syslog_facility = LOG_LOCAL0;

static bool assign_syslog_facility(int newval,
                                    bool doit, GucSource source);
static const char *assign_syslog_ident(const char *ident,
                                        bool doit, GucSource source);
#endif

static bool assign_session_replication_role(int newval, bool doit,
                                                                GucSource source);
static const char *show_num_temp_buffers(void);
static bool assign_phony_autocommit(bool newval, bool doit, GucSource source);
static const char *assign_custom_variable_classes(const char *newval, bool doit,
                                                           GucSource source);
static bool assign_debug_assertions(bool newval, bool doit, GucSource source);
static bool assign_ssl(bool newval, bool doit, GucSource source);
static bool assign_stage_log_stats(bool newval, bool doit, GucSource source);
static bool assign_log_stats(bool newval, bool doit, GucSource source);
static bool assign_transaction_read_only(bool newval, bool doit, GucSource source);
static const char *assign_canonical_path(const char *newval, bool doit, GucSource source);
static const char *assign_timezone_abbreviations(const char *newval, bool doit, GucSource source);
static const char *show_archive_command(void);
static bool assign_tcp_keepalives_idle(int newval, bool doit, GucSource source);
static bool assign_tcp_keepalives_interval(int newval, bool doit, GucSource source);
static bool assign_tcp_keepalives_count(int newval, bool doit, GucSource source);
static const char *show_tcp_keepalives_idle(void);
static const char *show_tcp_keepalives_interval(void);
static const char *show_tcp_keepalives_count(void);
static bool assign_maxconnections(int newval, bool doit, GucSource source);
static bool assign_autovacuum_max_workers(int newval, bool doit, GucSource source);
static bool assign_effective_io_concurrency(int newval, bool doit, GucSource source);
static const char *assign_pgstat_temp_directory(const char *newval, bool doit, GucSource source);

static char *config_enum_get_options(struct config_enum *record, 
                                                                         const char *prefix, const char *suffix,
                                                                         const char *separator);


/*
 * Options for enum values defined in this module.
 *
 * NOTE! Option values may not contain double quotes!
 */

/*
 * We have different sets for client and server message level options because
 * they sort slightly different (see "log" level)
 */
static const struct config_enum_entry client_message_level_options[] = {
        {"debug", DEBUG2, true},
        {"debug5", DEBUG5, false},
        {"debug4", DEBUG4, false},
        {"debug3", DEBUG3, false},
        {"debug2", DEBUG2, false},
        {"debug1", DEBUG1, false},
        {"log", LOG, false},
        {"info", INFO, true},
        {"notice", NOTICE, false},
        {"warning", WARNING, false},
        {"error", ERROR, false},
        {"fatal", FATAL, true},
        {"panic", PANIC, true},
        {NULL, 0, false}
};

static const struct config_enum_entry server_message_level_options[] = {
        {"debug", DEBUG2, true},
        {"debug5", DEBUG5, false},
        {"debug4", DEBUG4, false},
        {"debug3", DEBUG3, false},
        {"debug2", DEBUG2, false},
        {"debug1", DEBUG1, false},
        {"info", INFO, false},
        {"notice", NOTICE, false},
        {"warning", WARNING, false},
        {"error", ERROR, false},
        {"log", LOG, false},
        {"fatal", FATAL, false},
        {"panic", PANIC, false},
        {NULL, 0, false}
};

static const struct config_enum_entry intervalstyle_options[] = {
        {"postgres", INTSTYLE_POSTGRES, false},
        {"postgres_verbose", INTSTYLE_POSTGRES_VERBOSE, false},
        {"sql_standard", INTSTYLE_SQL_STANDARD, false},
        {"iso_8601", INTSTYLE_ISO_8601, false},
        {NULL, 0, false}
};

static const struct config_enum_entry log_error_verbosity_options[] = {
        {"terse", PGERROR_TERSE, false},
        {"default", PGERROR_DEFAULT, false},
        {"verbose", PGERROR_VERBOSE, false},
        {NULL, 0, false}
};

static const struct config_enum_entry log_statement_options[] = {
        {"none", LOGSTMT_NONE, false},
        {"ddl", LOGSTMT_DDL, false},
        {"mod", LOGSTMT_MOD, false},
        {"all", LOGSTMT_ALL, false},
        {NULL, 0, false}
};

static const struct config_enum_entry regex_flavor_options[] = {
    {"advanced", REG_ADVANCED, false},
    {"extended", REG_EXTENDED, false},
    {"basic", REG_BASIC, false},
    {NULL, 0, false}
};

static const struct config_enum_entry isolation_level_options[] = {
        {"serializable", XACT_SERIALIZABLE, false},
        {"repeatable read", XACT_REPEATABLE_READ, false},
        {"read committed", XACT_READ_COMMITTED, false},
        {"read uncommitted", XACT_READ_UNCOMMITTED, false},
        {NULL, 0}
};

static const struct config_enum_entry session_replication_role_options[] = {
        {"origin", SESSION_REPLICATION_ROLE_ORIGIN, false},
        {"replica", SESSION_REPLICATION_ROLE_REPLICA, false},
        {"local", SESSION_REPLICATION_ROLE_LOCAL, false},
        {NULL, 0, false}
};

#ifdef HAVE_SYSLOG
static const struct config_enum_entry syslog_facility_options[] = {
        {"local0", LOG_LOCAL0, false},
        {"local1", LOG_LOCAL1, false},
        {"local2", LOG_LOCAL2, false},
        {"local3", LOG_LOCAL3, false},
        {"local4", LOG_LOCAL4, false},
        {"local5", LOG_LOCAL5, false},
        {"local6", LOG_LOCAL6, false},
        {"local7", LOG_LOCAL7, false},
        {NULL, 0}
};
#endif

static const struct config_enum_entry track_function_options[] = {
        {"none", TRACK_FUNC_OFF, false},
        {"pl", TRACK_FUNC_PL, false},
        {"all", TRACK_FUNC_ALL, false},
        {NULL, 0, false}
};

static const struct config_enum_entry xmlbinary_options[] = {
        {"base64", XMLBINARY_BASE64, false},
        {"hex", XMLBINARY_HEX, false},
        {NULL, 0, false}
};

static const struct config_enum_entry xmloption_options[] = {
        {"content", XMLOPTION_CONTENT, false},
        {"document", XMLOPTION_DOCUMENT, false},
        {NULL, 0, false}
};

/*
 * Although only "on", "off", and "safe_encoding" are documented, we
 * accept all the likely variants of "on" and "off".
 */
static const struct config_enum_entry backslash_quote_options[] = {
        {"safe_encoding", BACKSLASH_QUOTE_SAFE_ENCODING, false},
        {"on", BACKSLASH_QUOTE_ON, false},
        {"off", BACKSLASH_QUOTE_OFF, false},
        {"true", BACKSLASH_QUOTE_ON, true},
        {"false", BACKSLASH_QUOTE_OFF, true},
        {"yes", BACKSLASH_QUOTE_ON, true},
        {"no", BACKSLASH_QUOTE_OFF, true},
        {"1", BACKSLASH_QUOTE_ON, true},
        {"0", BACKSLASH_QUOTE_OFF, true},
        {NULL, 0, false}
};

/*
 * Although only "on", "off", and "partition" are documented, we
 * accept all the likely variants of "on" and "off".
 */
static const struct config_enum_entry constraint_exclusion_options[] = {
        {"partition", CONSTRAINT_EXCLUSION_PARTITION, false},
        {"on", CONSTRAINT_EXCLUSION_ON, false},
        {"off", CONSTRAINT_EXCLUSION_OFF, false},
        {"true", CONSTRAINT_EXCLUSION_ON, true},
        {"false", CONSTRAINT_EXCLUSION_OFF, true},
        {"yes", CONSTRAINT_EXCLUSION_ON, true},
        {"no", CONSTRAINT_EXCLUSION_OFF, true},
        {"1", CONSTRAINT_EXCLUSION_ON, true},
        {"0", CONSTRAINT_EXCLUSION_OFF, true},
        {NULL, 0, false}
};

/*
 * Options for enum values stored in other modules
 */
extern const struct config_enum_entry sync_method_options[];

/*
 * GUC option variables that are exported from this module
 */
#ifdef USE_ASSERT_CHECKING
bool            assert_enabled = true;
#else
bool            assert_enabled = false;
#endif
bool            log_duration = false;
bool            Debug_print_plan = false;
bool            Debug_print_parse = false;
bool            Debug_print_rewritten = false;
bool            Debug_pretty_print = true;

bool            log_parser_stats = false;
bool            log_planner_stats = false;
bool            log_executor_stats = false;
bool            log_statement_stats = false;            /* this is sort of all three
                                                                                                 * above together */
bool            log_btree_build_stats = false;

bool            check_function_bodies = true;
bool            default_with_oids = false;
bool            SQL_inheritance = true;

bool            Password_encryption = true;

int                     log_min_error_statement = ERROR;
int                     log_min_messages = WARNING;
int                     client_min_messages = NOTICE;
int                     log_min_duration_statement = -1;
int                     log_temp_files = -1;

int                     num_temp_buffers = 1000;

char       *ConfigFileName;
char       *HbaFileName;
char       *IdentFileName;
char       *external_pid_file;

char       *pgstat_temp_directory;

int                     tcp_keepalives_idle;
int                     tcp_keepalives_interval;
int                     tcp_keepalives_count;

/*
 * These variables are all dummies that don't do anything, except in some
 * cases provide the value for SHOW to display.  The real state is elsewhere
 * and is kept in sync by assign_hooks.
 */
static char *log_destination_string;

#ifdef HAVE_SYSLOG
static char *syslog_ident_str;
#endif
static bool phony_autocommit;
static bool session_auth_is_superuser;
static double phony_random_seed;
static char *client_encoding_string;
static char *datestyle_string;
static char *locale_collate;
static char *locale_ctype;
static char *server_encoding_string;
static char *server_version_string;
static int      server_version_num;
static char *timezone_string;
static char *log_timezone_string;
static char *timezone_abbreviations_string;
static char *XactIsoLevel_string;
static char *data_directory;
static char *custom_variable_classes;
static int      max_function_args;
static int      max_index_keys;
static int      max_identifier_length;
static int      block_size;
static int      segment_size;
static int      wal_block_size;
static int      wal_segment_size;
static bool integer_datetimes;
static int      effective_io_concurrency;

/* should be static, but commands/variable.c needs to get at these */
char       *role_string;
char       *session_authorization_string;


/*
 * Displayable names for context types (enum GucContext)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const GucContext_Names[] =
{
         /* PGC_INTERNAL */ "internal",
         /* PGC_POSTMASTER */ "postmaster",
         /* PGC_SIGHUP */ "sighup",
         /* PGC_BACKEND */ "backend",
         /* PGC_SUSET */ "superuser",
         /* PGC_USERSET */ "user"
};

/*
 * Displayable names for source types (enum GucSource)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const GucSource_Names[] =
{
         /* PGC_S_DEFAULT */ "default",
         /* PGC_S_ENV_VAR */ "environment variable",
         /* PGC_S_FILE */ "configuration file",
         /* PGC_S_ARGV */ "command line",
         /* PGC_S_DATABASE */ "database",
         /* PGC_S_USER */ "user",
         /* PGC_S_CLIENT */ "client",
         /* PGC_S_OVERRIDE */ "override",
         /* PGC_S_INTERACTIVE */ "interactive",
         /* PGC_S_TEST */ "test",
         /* PGC_S_SESSION */ "session"
};

/*
 * Displayable names for the groupings defined in enum config_group
 */
const char *const config_group_names[] =
{
        /* UNGROUPED */
        gettext_noop("Ungrouped"),
        /* FILE_LOCATIONS */
        gettext_noop("File Locations"),
        /* CONN_AUTH */
        gettext_noop("Connections and Authentication"),
        /* CONN_AUTH_SETTINGS */
        gettext_noop("Connections and Authentication / Connection Settings"),
        /* CONN_AUTH_SECURITY */
        gettext_noop("Connections and Authentication / Security and Authentication"),
        /* RESOURCES */
        gettext_noop("Resource Usage"),
        /* RESOURCES_MEM */
        gettext_noop("Resource Usage / Memory"),
        /* RESOURCES_KERNEL */
        gettext_noop("Resource Usage / Kernel Resources"),
        /* WAL */
        gettext_noop("Write-Ahead Log"),
        /* WAL_SETTINGS */
        gettext_noop("Write-Ahead Log / Settings"),
        /* WAL_CHECKPOINTS */
        gettext_noop("Write-Ahead Log / Checkpoints"),
        /* QUERY_TUNING */
        gettext_noop("Query Tuning"),
        /* QUERY_TUNING_METHOD */
        gettext_noop("Query Tuning / Planner Method Configuration"),
        /* QUERY_TUNING_COST */
        gettext_noop("Query Tuning / Planner Cost Constants"),
        /* QUERY_TUNING_GEQO */
        gettext_noop("Query Tuning / Genetic Query Optimizer"),
        /* QUERY_TUNING_OTHER */
        gettext_noop("Query Tuning / Other Planner Options"),
        /* LOGGING */
        gettext_noop("Reporting and Logging"),
        /* LOGGING_WHERE */
        gettext_noop("Reporting and Logging / Where to Log"),
        /* LOGGING_WHEN */
        gettext_noop("Reporting and Logging / When to Log"),
        /* LOGGING_WHAT */
        gettext_noop("Reporting and Logging / What to Log"),
        /* STATS */
        gettext_noop("Statistics"),
        /* STATS_MONITORING */
        gettext_noop("Statistics / Monitoring"),
        /* STATS_COLLECTOR */
        gettext_noop("Statistics / Query and Index Statistics Collector"),
        /* AUTOVACUUM */
        gettext_noop("Autovacuum"),
        /* CLIENT_CONN */
        gettext_noop("Client Connection Defaults"),
        /* CLIENT_CONN_STATEMENT */
        gettext_noop("Client Connection Defaults / Statement Behavior"),
        /* CLIENT_CONN_LOCALE */
        gettext_noop("Client Connection Defaults / Locale and Formatting"),
        /* CLIENT_CONN_OTHER */
        gettext_noop("Client Connection Defaults / Other Defaults"),
        /* LOCK_MANAGEMENT */
        gettext_noop("Lock Management"),
        /* COMPAT_OPTIONS */
        gettext_noop("Version and Platform Compatibility"),
        /* COMPAT_OPTIONS_PREVIOUS */
        gettext_noop("Version and Platform Compatibility / Previous PostgreSQL Versions"),
        /* COMPAT_OPTIONS_CLIENT */
        gettext_noop("Version and Platform Compatibility / Other Platforms and Clients"),
        /* PRESET_OPTIONS */
        gettext_noop("Preset Options"),
        /* CUSTOM_OPTIONS */
        gettext_noop("Customized Options"),
        /* DEVELOPER_OPTIONS */
        gettext_noop("Developer Options"),
        /* help_config wants this array to be null-terminated */
        NULL
};

/*
 * Displayable names for GUC variable types (enum config_type)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const config_type_names[] =
{
         /* PGC_BOOL */ "bool",
         /* PGC_INT */ "integer",
         /* PGC_REAL */ "real",
         /* PGC_STRING */ "string",
         /* PGC_ENUM */ "enum"
};


/*
 * Contents of GUC tables
 *
 * See src/backend/utils/misc/README for design notes.
 *
 * TO ADD AN OPTION:
 *
 * 1. Declare a global variable of type bool, int, double, or char*
 *        and make use of it.
 *
 * 2. Decide at what times it's safe to set the option. See guc.h for
 *        details.
 *
 * 3. Decide on a name, a default value, upper and lower bounds (if
 *        applicable), etc.
 *
 * 4. Add a record below.
 *
 * 5. Add it to src/backend/utils/misc/postgresql.conf.sample, if
 *        appropriate.
 *
 * 6. Don't forget to document the option (at least in config.sgml).
 *
 * 7. If it's a new GUC_LIST option you must edit pg_dumpall.c to ensure
 *        it is not single quoted at dump time.
 */


/******** option records follow ********/

static struct config_bool ConfigureNamesBool[] =
{
        {
                {"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of sequential-scan plans."),
                        NULL
                },
                &enable_seqscan,
                true, NULL, NULL
        },
        {
                {"enable_indexscan", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of index-scan plans."),
                        NULL
                },
                &enable_indexscan,
                true, NULL, NULL
        },
        {
                {"enable_bitmapscan", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of bitmap-scan plans."),
                        NULL
                },
                &enable_bitmapscan,
                true, NULL, NULL
        },
        {
                {"enable_tidscan", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of TID scan plans."),
                        NULL
                },
                &enable_tidscan,
                true, NULL, NULL
        },
        {
                {"enable_sort", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of explicit sort steps."),
                        NULL
                },
                &enable_sort,
                true, NULL, NULL
        },
        {
                {"enable_hashagg", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of hashed aggregation plans."),
                        NULL
                },
                &enable_hashagg,
                true, NULL, NULL
        },
        {
                {"enable_nestloop", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of nested-loop join plans."),
                        NULL
                },
                &enable_nestloop,
                true, NULL, NULL
        },
        {
                {"enable_mergejoin", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of merge join plans."),
                        NULL
                },
                &enable_mergejoin,
                true, NULL, NULL
        },
        {
                {"enable_hashjoin", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enables the planner's use of hash join plans."),
                        NULL
                },
                &enable_hashjoin,
                true, NULL, NULL
        },
        {
                {"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("Enables genetic query optimization."),
                        gettext_noop("This algorithm attempts to do planning without "
                                                 "exhaustive searching.")
                },
                &enable_geqo,
                true, NULL, NULL
        },
        {
                /* Not for general use --- used by SET SESSION AUTHORIZATION */
                {"is_superuser", PGC_INTERNAL, UNGROUPED,
                        gettext_noop("Shows whether the current user is a superuser."),
                        NULL,
                        GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &session_auth_is_superuser,
                false, NULL, NULL
        },
        {
                {"ssl", PGC_POSTMASTER, CONN_AUTH_SECURITY,
                        gettext_noop("Enables SSL connections."),
                        NULL
                },
                &EnableSSL,
                false, assign_ssl, NULL
        },
        {
                {"fsync", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("Forces synchronization of updates to disk."),
                        gettext_noop("The server will use the fsync() system call in several places to make "
                        "sure that updates are physically written to disk. This insures "
                                                 "that a database cluster will recover to a consistent state after "
                                                 "an operating system or hardware crash.")
                },
                &enableFsync,
                true, NULL, NULL
        },
        {
                {"synchronous_commit", PGC_USERSET, WAL_SETTINGS,
                        gettext_noop("Sets immediate fsync at commit."),
                        NULL
                },
                &XactSyncCommit,
                true, NULL, NULL
        },
        {
                {"zero_damaged_pages", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("Continues processing past damaged page headers."),
                        gettext_noop("Detection of a damaged page header normally causes PostgreSQL to "
                                "report an error, aborting the current transaction. Setting "
                                                 "zero_damaged_pages to true causes the system to instead report a "
                                                 "warning, zero out the damaged page, and continue processing. This "
                                                 "behavior will destroy data, namely all the rows on the damaged page."),
                        GUC_NOT_IN_SAMPLE
                },
                &zero_damaged_pages,
                false, NULL, NULL
        },
        {
                {"full_page_writes", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("Writes full pages to WAL when first modified after a checkpoint."),
                        gettext_noop("A page write in process during an operating system crash might be "
                                                 "only partially written to disk.  During recovery, the row changes "
                          "stored in WAL are not enough to recover.  This option writes "
                                                 "pages when first modified after a checkpoint to WAL so full recovery "
                                                 "is possible.")
                },
                &fullPageWrites,
                true, NULL, NULL
        },
        {
                {"silent_mode", PGC_POSTMASTER, LOGGING_WHEN,
                        gettext_noop("Runs the server silently."),
                        gettext_noop("If this parameter is set, the server will automatically run in the "
                                 "background and any controlling terminals are dissociated.")
                },
                &SilentMode,
                false, NULL, NULL
        },
        {
                {"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
                        gettext_noop("Logs each checkpoint."),
                        NULL
                },
                &log_checkpoints,
                false, NULL, NULL
        },
        {
                {"log_connections", PGC_BACKEND, LOGGING_WHAT,
                        gettext_noop("Logs each successful connection."),
                        NULL
                },
                &Log_connections,
                false, NULL, NULL
        },
        {
                {"log_disconnections", PGC_BACKEND, LOGGING_WHAT,
                        gettext_noop("Logs end of a session, including duration."),
                        NULL
                },
                &Log_disconnections,
                false, NULL, NULL
        },
        {
                {"debug_assertions", PGC_USERSET, DEVELOPER_OPTIONS,
                        gettext_noop("Turns on various assertion checks."),
                        gettext_noop("This is a debugging aid."),
                        GUC_NOT_IN_SAMPLE
                },
                &assert_enabled,
#ifdef USE_ASSERT_CHECKING
                true,
#else
                false,
#endif
                assign_debug_assertions, NULL
        },
        {
                /* currently undocumented, so don't show in SHOW ALL */
                {"exit_on_error", PGC_USERSET, UNGROUPED,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE
                },
                &ExitOnAnyError,
                false, NULL, NULL
        },
        {
                {"log_duration", PGC_SUSET, LOGGING_WHAT,
                        gettext_noop("Logs the duration of each completed SQL statement."),
                        NULL
                },
                &log_duration,
                false, NULL, NULL
        },
        {
                {"debug_print_parse", PGC_USERSET, LOGGING_WHAT,
                        gettext_noop("Logs each query's parse tree."),
                        NULL
                },
                &Debug_print_parse,
                false, NULL, NULL
        },
        {
                {"debug_print_rewritten", PGC_USERSET, LOGGING_WHAT,
                        gettext_noop("Logs each query's rewritten parse tree."),
                        NULL
                },
                &Debug_print_rewritten,
                false, NULL, NULL
        },
        {
                {"debug_print_plan", PGC_USERSET, LOGGING_WHAT,
                        gettext_noop("Logs each query's execution plan."),
                        NULL
                },
                &Debug_print_plan,
                false, NULL, NULL
        },
        {
                {"debug_pretty_print", PGC_USERSET, LOGGING_WHAT,
                        gettext_noop("Indents parse and plan tree displays."),
                        NULL
                },
                &Debug_pretty_print,
                true, NULL, NULL
        },
        {
                {"log_parser_stats", PGC_SUSET, STATS_MONITORING,
                        gettext_noop("Writes parser performance statistics to the server log."),
                        NULL
                },
                &log_parser_stats,
                false, assign_stage_log_stats, NULL
        },
        {
                {"log_planner_stats", PGC_SUSET, STATS_MONITORING,
                        gettext_noop("Writes planner performance statistics to the server log."),
                        NULL
                },
                &log_planner_stats,
                false, assign_stage_log_stats, NULL
        },
        {
                {"log_executor_stats", PGC_SUSET, STATS_MONITORING,
                        gettext_noop("Writes executor performance statistics to the server log."),
                        NULL
                },
                &log_executor_stats,
                false, assign_stage_log_stats, NULL
        },
        {
                {"log_statement_stats", PGC_SUSET, STATS_MONITORING,
                        gettext_noop("Writes cumulative performance statistics to the server log."),
                        NULL
                },
                &log_statement_stats,
                false, assign_log_stats, NULL
        },
#ifdef BTREE_BUILD_STATS
        {
                {"log_btree_build_stats", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &log_btree_build_stats,
                false, NULL, NULL
        },
#endif

        {
                {"track_activities", PGC_SUSET, STATS_COLLECTOR,
                        gettext_noop("Collects information about executing commands."),
                        gettext_noop("Enables the collection of information on the currently "
                                                 "executing command of each session, along with "
                                                 "the time at which that command began execution.")
                },
                &pgstat_track_activities,
                true, NULL, NULL
        },
        {
                {"track_counts", PGC_SUSET, STATS_COLLECTOR,
                        gettext_noop("Collects statistics on database activity."),
                        NULL
                },
                &pgstat_track_counts,
                true, NULL, NULL
        },

        {
                {"update_process_title", PGC_SUSET, STATS_COLLECTOR,
                        gettext_noop("Updates the process title to show the active SQL command."),
                        gettext_noop("Enables updating of the process title every time a new SQL command is received by the server.")
                },
                &update_process_title,
                true, NULL, NULL
        },

        {
                {"autovacuum", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Starts the autovacuum subprocess."),
                        NULL
                },
                &autovacuum_start_daemon,
                true, NULL, NULL
        },

        {
                {"trace_notify", PGC_USERSET, DEVELOPER_OPTIONS,
                        gettext_noop("Generates debugging output for LISTEN and NOTIFY."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_notify,
                false, NULL, NULL
        },

#ifdef LOCK_DEBUG
        {
                {"trace_locks", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_locks,
                false, NULL, NULL
        },
        {
                {"trace_userlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_userlocks,
                false, NULL, NULL
        },
        {
                {"trace_lwlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_lwlocks,
                false, NULL, NULL
        },
        {
                {"debug_deadlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Debug_deadlocks,
                false, NULL, NULL
        },
#endif

        {
                {"log_lock_waits", PGC_SUSET, LOGGING_WHAT,
                        gettext_noop("Logs long lock waits."),
                        NULL
                },
                &log_lock_waits,
                false, NULL, NULL
        },

        {
                {"log_hostname", PGC_SIGHUP, LOGGING_WHAT,
                        gettext_noop("Logs the host name in the connection logs."),
                        gettext_noop("By default, connection logs only show the IP address "
                                                 "of the connecting host. If you want them to show the host name you "
                          "can turn this on, but depending on your host name resolution "
                           "setup it might impose a non-negligible performance penalty.")
                },
                &log_hostname,
                false, NULL, NULL
        },
        {
                {"sql_inheritance", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Causes subtables to be included by default in various commands."),
                        NULL
                },
                &SQL_inheritance,
                true, NULL, NULL
        },
        {
                {"password_encryption", PGC_USERSET, CONN_AUTH_SECURITY,
                        gettext_noop("Encrypt passwords."),
                        gettext_noop("When a password is specified in CREATE USER or "
                           "ALTER USER without writing either ENCRYPTED or UNENCRYPTED, "
                                                 "this parameter determines whether the password is to be encrypted.")
                },
                &Password_encryption,
                true, NULL, NULL
        },
        {
                {"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT,
                        gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."),
                        gettext_noop("When turned on, expressions of the form expr = NULL "
                           "(or NULL = expr) are treated as expr IS NULL, that is, they "
                                "return true if expr evaluates to the null value, and false "
                           "otherwise. The correct behavior of expr = NULL is to always "
                                                 "return null (unknown).")
                },
                &Transform_null_equals,
                false, NULL, NULL
        },
        {
                {"db_user_namespace", PGC_SIGHUP, CONN_AUTH_SECURITY,
                        gettext_noop("Enables per-database user names."),
                        NULL
                },
                &Db_user_namespace,
                false, NULL, NULL
        },
        {
                /* only here for backwards compatibility */
                {"autocommit", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("This parameter doesn't do anything."),
                        gettext_noop("It's just here so that we won't choke on SET AUTOCOMMIT TO ON from 7.3-vintage clients."),
                        GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE
                },
                &phony_autocommit,
                true, assign_phony_autocommit, NULL
        },
        {
                {"default_transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the default read-only status of new transactions."),
                        NULL
                },
                &DefaultXactReadOnly,
                false, NULL, NULL
        },
        {
                {"transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the current transaction's read-only status."),
                        NULL,
                        GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &XactReadOnly,
                false, assign_transaction_read_only, NULL
        },
        {
                {"add_missing_from", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Automatically adds missing table references to FROM clauses."),
                        NULL
                },
                &add_missing_from,
                false, NULL, NULL
        },
        {
                {"check_function_bodies", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Check function bodies during CREATE FUNCTION."),
                        NULL
                },
                &check_function_bodies,
                true, NULL, NULL
        },
        {
                {"array_nulls", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Enable input of NULL elements in arrays."),
                        gettext_noop("When turned on, unquoted NULL in an array input "
                                                 "value means a null value; "
                                                 "otherwise it is taken literally.")
                },
                &Array_nulls,
                true, NULL, NULL
        },
        {
                {"default_with_oids", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Create new tables with OIDs by default."),
                        NULL
                },
                &default_with_oids,
                false, NULL, NULL
        },
        {
                {"logging_collector", PGC_POSTMASTER, LOGGING_WHERE,
                        gettext_noop("Start a subprocess to capture stderr output and/or csvlogs into log files."),
                        NULL
                },
                &Logging_collector,
                false, NULL, NULL
        },
        {
                {"log_truncate_on_rotation", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Truncate existing log files of same name during log rotation."),
                        NULL
                },
                &Log_truncate_on_rotation,
                false, NULL, NULL
        },

#ifdef TRACE_SORT
        {
                {"trace_sort", PGC_USERSET, DEVELOPER_OPTIONS,
                        gettext_noop("Emit information about resource usage in sorting."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &trace_sort,
                false, NULL, NULL
        },
#endif

#ifdef TRACE_SYNCSCAN
        /* this is undocumented because not exposed in a standard build */
        {
                {"trace_syncscan", PGC_USERSET, DEVELOPER_OPTIONS,
                        gettext_noop("Generate debugging output for synchronized scanning."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &trace_syncscan,
                false, NULL, NULL
        },
#endif

#ifdef DEBUG_BOUNDED_SORT
        /* this is undocumented because not exposed in a standard build */
        {
                {
                        "optimize_bounded_sort", PGC_USERSET, QUERY_TUNING_METHOD,
                        gettext_noop("Enable bounded sorting using heap sort."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &optimize_bounded_sort,
                true, NULL, NULL
        },
#endif

#ifdef WAL_DEBUG
        {
                {"wal_debug", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("Emit WAL-related debugging output."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &XLOG_DEBUG,
                false, NULL, NULL
        },
#endif

        {
                {"integer_datetimes", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Datetimes are integer based."),
                        NULL,
                        GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &integer_datetimes,
#ifdef HAVE_INT64_TIMESTAMP
                true, NULL, NULL
#else
                false, NULL, NULL
#endif
        },

        {
                {"krb_caseins_users", PGC_SIGHUP, CONN_AUTH_SECURITY,
                        gettext_noop("Sets whether Kerberos and GSSAPI user names should be treated as case-insensitive."),
                        NULL
                },
                &pg_krb_caseins_users,
                false, NULL, NULL
        },

        {
                {"escape_string_warning", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Warn about backslash escapes in ordinary string literals."),
                        NULL
                },
                &escape_string_warning,
                true, NULL, NULL
        },

        {
                {"standard_conforming_strings", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Causes '...' strings to treat backslashes literally."),
                        NULL,
                        GUC_REPORT
                },
                &standard_conforming_strings,
                false, NULL, NULL
        },

        {
                {"synchronize_seqscans", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Enable synchronized sequential scans."),
                        NULL
                },
                &synchronize_seqscans,
                true, NULL, NULL
        },

        {
                {"archive_mode", PGC_POSTMASTER, WAL_SETTINGS,
                        gettext_noop("Allows archiving of WAL files using archive_command."),
                        NULL
                },
                &XLogArchiveMode,
                false, NULL, NULL
        },

        {
                {"allow_system_table_mods", PGC_POSTMASTER, DEVELOPER_OPTIONS,
                        gettext_noop("Allows modifications of the structure of system tables."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &allowSystemTableMods,
                false, NULL, NULL
        },

        {
                {"ignore_system_indexes", PGC_BACKEND, DEVELOPER_OPTIONS,
                        gettext_noop("Disables reading from system indexes."),
                        gettext_noop("It does not prevent updating the indexes, so it is safe "
                                                 "to use.  The worst consequence is slowness."),
                        GUC_NOT_IN_SAMPLE
                },
                &IgnoreSystemIndexes,
                false, NULL, NULL
        },

        /* End-of-list marker */
        {
                {NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL
        }
};


static struct config_int ConfigureNamesInt[] =
{
        {
                {"archive_timeout", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("Forces a switch to the next xlog file if a "
                                                 "new file has not been started within N seconds."),
                        NULL,
                        GUC_UNIT_S
                },
                &XLogArchiveTimeout,
                0, 0, INT_MAX, NULL, NULL
        },
        {
                {"post_auth_delay", PGC_BACKEND, DEVELOPER_OPTIONS,
                        gettext_noop("Waits N seconds on connection startup after authentication."),
                        gettext_noop("This allows attaching a debugger to the process."),
                        GUC_NOT_IN_SAMPLE | GUC_UNIT_S
                },
                &PostAuthDelay,
                0, 0, INT_MAX, NULL, NULL
        },
        {
                {"default_statistics_target", PGC_USERSET, QUERY_TUNING_OTHER,
                        gettext_noop("Sets the default statistics target."),
                        gettext_noop("This applies to table columns that have not had a "
                                "column-specific target set via ALTER TABLE SET STATISTICS.")
                },
                &default_statistics_target,
                100, 1, 10000, NULL, NULL
        },
        {
                {"from_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
                        gettext_noop("Sets the FROM-list size beyond which subqueries "
                                                 "are not collapsed."),
                        gettext_noop("The planner will merge subqueries into upper "
                                "queries if the resulting FROM list would have no more than "
                                                 "this many items.")
                },
                &from_collapse_limit,
                8, 1, INT_MAX, NULL, NULL
        },
        {
                {"join_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
                        gettext_noop("Sets the FROM-list size beyond which JOIN "
                                                 "constructs are not flattened."),
                        gettext_noop("The planner will flatten explicit JOIN "
                                                 "constructs into lists of FROM items whenever a "
                                                 "list of no more than this many items would result.")
                },
                &join_collapse_limit,
                8, 1, INT_MAX, NULL, NULL
        },
        {
                {"geqo_threshold", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("Sets the threshold of FROM items beyond which GEQO is used."),
                        NULL
                },
                &geqo_threshold,
                12, 2, INT_MAX, NULL, NULL
        },
        {
                {"geqo_effort", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("GEQO: effort is used to set the default for other GEQO parameters."),
                        NULL
                },
                &Geqo_effort,
                DEFAULT_GEQO_EFFORT, MIN_GEQO_EFFORT, MAX_GEQO_EFFORT, NULL, NULL
        },
        {
                {"geqo_pool_size", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("GEQO: number of individuals in the population."),
                        gettext_noop("Zero selects a suitable default value.")
                },
                &Geqo_pool_size,
                0, 0, INT_MAX, NULL, NULL
        },
        {
                {"geqo_generations", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("GEQO: number of iterations of the algorithm."),
                        gettext_noop("Zero selects a suitable default value.")
                },
                &Geqo_generations,
                0, 0, INT_MAX, NULL, NULL
        },

        {
                /* This is PGC_SIGHUP so all backends have the same value. */
                {"deadlock_timeout", PGC_SIGHUP, LOCK_MANAGEMENT,
                        gettext_noop("Sets the time to wait on a lock before checking for deadlock."),
                        NULL,
                        GUC_UNIT_MS
                },
                &DeadlockTimeout,
                1000, 1, INT_MAX / 1000, NULL, NULL
        },

        /*
         * Note: MaxBackends is limited to INT_MAX/4 because some places compute
         * 4*MaxBackends without any overflow check.  This check is made in
         * assign_maxconnections, since MaxBackends is computed as MaxConnections
         * plus autovacuum_max_workers.
         *
         * Likewise we have to limit NBuffers to INT_MAX/2.
         */
        {
                {"max_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the maximum number of concurrent connections."),
                        NULL
                },
                &MaxConnections,
                100, 1, INT_MAX / 4, assign_maxconnections, NULL
        },

        {
                {"superuser_reserved_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the number of connection slots reserved for superusers."),
                        NULL
                },
                &ReservedBackends,
                3, 0, INT_MAX / 4, NULL, NULL
        },

        {
                {"shared_buffers", PGC_POSTMASTER, RESOURCES_MEM,
                        gettext_noop("Sets the number of shared memory buffers used by the server."),
                        NULL,
                        GUC_UNIT_BLOCKS
                },
                &NBuffers,
                1024, 16, INT_MAX / 2, NULL, NULL
        },

        {
                {"temp_buffers", PGC_USERSET, RESOURCES_MEM,
                        gettext_noop("Sets the maximum number of temporary buffers used by each session."),
                        NULL,
                        GUC_UNIT_BLOCKS
                },
                &num_temp_buffers,
                1024, 100, INT_MAX / 2, NULL, show_num_temp_buffers
        },

        {
                {"port", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the TCP port the server listens on."),
                        NULL
                },
                &PostPortNumber,
                DEF_PGPORT, 1, 65535, NULL, NULL
        },

        {
                {"unix_socket_permissions", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the access permissions of the Unix-domain socket."),
                        gettext_noop("Unix-domain sockets use the usual Unix file system "
                                                 "permission set. The parameter value is expected to be a numeric mode "
                                                 "specification in the form accepted by the chmod and umask system "
                                                 "calls. (To use the customary octal format the number must start with "
                                                 "a 0 (zero).)")
                },
                &Unix_socket_permissions,
                0777, 0000, 0777, NULL, NULL
        },

        {
                {"work_mem", PGC_USERSET, RESOURCES_MEM,
                        gettext_noop("Sets the maximum memory to be used for query workspaces."),
                        gettext_noop("This much memory can be used by each internal "
                                                 "sort operation and hash table before switching to "
                                                 "temporary disk files."),
                        GUC_UNIT_KB
                },
                &work_mem,
                1024, 64, MAX_KILOBYTES, NULL, NULL
        },

        {
                {"maintenance_work_mem", PGC_USERSET, RESOURCES_MEM,
                        gettext_noop("Sets the maximum memory to be used for maintenance operations."),
                        gettext_noop("This includes operations such as VACUUM and CREATE INDEX."),
                        GUC_UNIT_KB
                },
                &maintenance_work_mem,
                16384, 1024, MAX_KILOBYTES, NULL, NULL
        },

        {
                {"max_stack_depth", PGC_SUSET, RESOURCES_MEM,
                        gettext_noop("Sets the maximum stack depth, in kilobytes."),
                        NULL,
                        GUC_UNIT_KB
                },
                &max_stack_depth,
                100, 100, MAX_KILOBYTES, assign_max_stack_depth, NULL
        },

        {
                {"vacuum_cost_page_hit", PGC_USERSET, RESOURCES,
                        gettext_noop("Vacuum cost for a page found in the buffer cache."),
                        NULL
                },
                &VacuumCostPageHit,
                1, 0, 10000, NULL, NULL
        },

        {
                {"vacuum_cost_page_miss", PGC_USERSET, RESOURCES,
                        gettext_noop("Vacuum cost for a page not found in the buffer cache."),
                        NULL
                },
                &VacuumCostPageMiss,
                10, 0, 10000, NULL, NULL
        },

        {
                {"vacuum_cost_page_dirty", PGC_USERSET, RESOURCES,
                        gettext_noop("Vacuum cost for a page dirtied by vacuum."),
                        NULL
                },
                &VacuumCostPageDirty,
                20, 0, 10000, NULL, NULL
        },

        {
                {"vacuum_cost_limit", PGC_USERSET, RESOURCES,
                        gettext_noop("Vacuum cost amount available before napping."),
                        NULL
                },
                &VacuumCostLimit,
                200, 1, 10000, NULL, NULL
        },

        {
                {"vacuum_cost_delay", PGC_USERSET, RESOURCES,
                        gettext_noop("Vacuum cost delay in milliseconds."),
                        NULL,
                        GUC_UNIT_MS
                },
                &VacuumCostDelay,
                0, 0, 1000, NULL, NULL
        },

        {
                {"autovacuum_vacuum_cost_delay", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Vacuum cost delay in milliseconds, for autovacuum."),
                        NULL,
                        GUC_UNIT_MS
                },
                &autovacuum_vac_cost_delay,
                20, -1, 1000, NULL, NULL
        },

        {
                {"autovacuum_vacuum_cost_limit", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Vacuum cost amount available before napping, for autovacuum."),
                        NULL
                },
                &autovacuum_vac_cost_limit,
                -1, -1, 10000, NULL, NULL
        },

        {
                {"max_files_per_process", PGC_POSTMASTER, RESOURCES_KERNEL,
                        gettext_noop("Sets the maximum number of simultaneously open files for each server process."),
                        NULL
                },
                &max_files_per_process,
                1000, 25, INT_MAX, NULL, NULL
        },

        {
                {"max_prepared_transactions", PGC_POSTMASTER, RESOURCES,
                        gettext_noop("Sets the maximum number of simultaneously prepared transactions."),
                        NULL
                },
                &max_prepared_xacts,
                5, 0, INT_MAX, NULL, NULL
        },

#ifdef LOCK_DEBUG
        {
                {"trace_lock_oidmin", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_lock_oidmin,
                FirstNormalObjectId, 0, INT_MAX, NULL, NULL
        },
        {
                {"trace_lock_table", PGC_SUSET, DEVELOPER_OPTIONS,
                        gettext_noop("No description available."),
                        NULL,
                        GUC_NOT_IN_SAMPLE
                },
                &Trace_lock_table,
                0, 0, INT_MAX, NULL, NULL
        },
#endif

        {
                {"statement_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the maximum allowed duration of any statement."),
                        gettext_noop("A value of 0 turns off the timeout."),
                        GUC_UNIT_MS
                },
                &StatementTimeout,
                0, 0, INT_MAX, NULL, NULL
        },

        {
                {"vacuum_freeze_min_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Minimum age at which VACUUM should freeze a table row."),
                        NULL
                },
                &vacuum_freeze_min_age,
                50000000, 0, 1000000000, NULL, NULL
        },

        {
                {"vacuum_freeze_table_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Age at which VACUUM should scan whole table to freeze tuples."),
                        NULL
                },
                &vacuum_freeze_table_age,
                150000000, 0, 2000000000, NULL, NULL
        },

        {
                {"max_locks_per_transaction", PGC_POSTMASTER, LOCK_MANAGEMENT,
                        gettext_noop("Sets the maximum number of locks per transaction."),
                        gettext_noop("The shared lock table is sized on the assumption that "
                          "at most max_locks_per_transaction * max_connections distinct "
                                                 "objects will need to be locked at any one time.")
                },
                &max_locks_per_xact,
                64, 10, INT_MAX, NULL, NULL
        },

        {
                {"authentication_timeout", PGC_SIGHUP, CONN_AUTH_SECURITY,
                        gettext_noop("Sets the maximum allowed time to complete client authentication."),
                        NULL,
                        GUC_UNIT_S
                },
                &AuthenticationTimeout,
                60, 1, 600, NULL, NULL
        },

        {
                /* Not for general use */
                {"pre_auth_delay", PGC_SIGHUP, DEVELOPER_OPTIONS,
                        gettext_noop("Waits N seconds on connection startup before authentication."),
                        gettext_noop("This allows attaching a debugger to the process."),
                        GUC_NOT_IN_SAMPLE | GUC_UNIT_S
                },
                &PreAuthDelay,
                0, 0, 60, NULL, NULL
        },

        {
                {"checkpoint_segments", PGC_SIGHUP, WAL_CHECKPOINTS,
                        gettext_noop("Sets the maximum distance in log segments between automatic WAL checkpoints."),
                        NULL
                },
                &CheckPointSegments,
                3, 1, INT_MAX, NULL, NULL
        },

        {
                {"checkpoint_timeout", PGC_SIGHUP, WAL_CHECKPOINTS,
                        gettext_noop("Sets the maximum time between automatic WAL checkpoints."),
                        NULL,
                        GUC_UNIT_S
                },
                &CheckPointTimeout,
                300, 30, 3600, NULL, NULL
        },

        {
                {"checkpoint_warning", PGC_SIGHUP, WAL_CHECKPOINTS,
                        gettext_noop("Enables warnings if checkpoint segments are filled more "
                                                 "frequently than this."),
                        gettext_noop("Write a message to the server log if checkpoints "
                        "caused by the filling of checkpoint segment files happens more "
                                                 "frequently than this number of seconds. Zero turns off the warning."),
                        GUC_UNIT_S
                },
                &CheckPointWarning,
                30, 0, INT_MAX, NULL, NULL
        },

        {
                {"wal_buffers", PGC_POSTMASTER, WAL_SETTINGS,
                        gettext_noop("Sets the number of disk-page buffers in shared memory for WAL."),
                        NULL,
                        GUC_UNIT_XBLOCKS
                },
                &XLOGbuffers,
                8, 4, INT_MAX, NULL, NULL
        },

        {
                {"wal_writer_delay", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("WAL writer sleep time between WAL flushes."),
                        NULL,
                        GUC_UNIT_MS
                },
                &WalWriterDelay,
                200, 1, 10000, NULL, NULL
        },

        {
                {"commit_delay", PGC_USERSET, WAL_SETTINGS,
                        gettext_noop("Sets the delay in microseconds between transaction commit and "
                                                 "flushing WAL to disk."),
                        NULL
                },
                &CommitDelay,
                0, 0, 100000, NULL, NULL
        },

        {
                {"commit_siblings", PGC_USERSET, WAL_SETTINGS,
                        gettext_noop("Sets the minimum concurrent open transactions before performing "
                                                 "commit_delay."),
                        NULL
                },
                &CommitSiblings,
                5, 1, 1000, NULL, NULL
        },

        {
                {"extra_float_digits", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the number of digits displayed for floating-point values."),
                        gettext_noop("This affects real, double precision, and geometric data types. "
                         "The parameter value is added to the standard number of digits "
                                                 "(FLT_DIG or DBL_DIG as appropriate).")
                },
                &extra_float_digits,
                0, -15, 2, NULL, NULL
        },

        {
                {"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
                        gettext_noop("Sets the minimum execution time above which "
                                                 "statements will be logged."),
                        gettext_noop("Zero prints all queries. -1 turns this feature off."),
                        GUC_UNIT_MS
                },
                &log_min_duration_statement,
                -1, -1, INT_MAX / 1000, NULL, NULL
        },

        {
                {"log_autovacuum_min_duration", PGC_SIGHUP, LOGGING_WHAT,
                        gettext_noop("Sets the minimum execution time above which "
                                                 "autovacuum actions will be logged."),
                        gettext_noop("Zero prints all actions. -1 turns autovacuum logging off."),
                        GUC_UNIT_MS
                },
                &Log_autovacuum_min_duration,
                -1, -1, INT_MAX / 1000, NULL, NULL
        },

        {
                {"bgwriter_delay", PGC_SIGHUP, RESOURCES,
                        gettext_noop("Background writer sleep time between rounds."),
                        NULL,
                        GUC_UNIT_MS
                },
                &BgWriterDelay,
                200, 10, 10000, NULL, NULL
        },

        {
                {"bgwriter_lru_maxpages", PGC_SIGHUP, RESOURCES,
                        gettext_noop("Background writer maximum number of LRU pages to flush per round."),
                        NULL
                },
                &bgwriter_lru_maxpages,
                100, 0, 1000, NULL, NULL
        },

        {
                {"effective_io_concurrency", PGC_USERSET, RESOURCES,
                        gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
                        gettext_noop("For RAID arrays, this should be approximately the number of drive spindles in the array.")
                },
                &effective_io_concurrency,
#ifdef USE_PREFETCH
                1, 0, 1000,
#else
                0, 0, 0,
#endif
                assign_effective_io_concurrency, NULL
        },

        {
                {"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Automatic log file rotation will occur after N minutes."),
                        NULL,
                        GUC_UNIT_MIN
                },
                &Log_RotationAge,
                HOURS_PER_DAY * MINS_PER_HOUR, 0, INT_MAX / MINS_PER_HOUR, NULL, NULL
        },

        {
                {"log_rotation_size", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Automatic log file rotation will occur after N kilobytes."),
                        NULL,
                        GUC_UNIT_KB
                },
                &Log_RotationSize,
                10 * 1024, 0, INT_MAX / 1024, NULL, NULL
        },

        {
                {"max_function_args", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the maximum number of function arguments."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &max_function_args,
                FUNC_MAX_ARGS, FUNC_MAX_ARGS, FUNC_MAX_ARGS, NULL, NULL
        },

        {
                {"max_index_keys", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the maximum number of index keys."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &max_index_keys,
                INDEX_MAX_KEYS, INDEX_MAX_KEYS, INDEX_MAX_KEYS, NULL, NULL
        },

        {
                {"max_identifier_length", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the maximum identifier length."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &max_identifier_length,
                NAMEDATALEN - 1, NAMEDATALEN - 1, NAMEDATALEN - 1, NULL, NULL
        },

        {
                {"block_size", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the size of a disk block."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &block_size,
                BLCKSZ, BLCKSZ, BLCKSZ, NULL, NULL
        },

        {
                {"segment_size", PGC_INTERNAL, PRESET_OPTIONS,
                    gettext_noop("Shows the number of pages per disk file."),
                    NULL,
                    GUC_UNIT_BLOCKS | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &segment_size,
                RELSEG_SIZE, RELSEG_SIZE, RELSEG_SIZE, NULL, NULL
        },

        {
                {"wal_block_size", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the block size in the write ahead log."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &wal_block_size,
                XLOG_BLCKSZ, XLOG_BLCKSZ, XLOG_BLCKSZ, NULL, NULL
        },

        {
                {"wal_segment_size", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the number of pages per write ahead log segment."),
                        NULL,
                        GUC_UNIT_XBLOCKS | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &wal_segment_size,
                (XLOG_SEG_SIZE / XLOG_BLCKSZ), 
                (XLOG_SEG_SIZE / XLOG_BLCKSZ), 
                (XLOG_SEG_SIZE / XLOG_BLCKSZ),
                NULL, NULL
        },

        {
                {"autovacuum_naptime", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Time to sleep between autovacuum runs."),
                        NULL,
                        GUC_UNIT_S
                },
                &autovacuum_naptime,
                60, 1, INT_MAX / 1000, NULL, NULL
        },
        {
                {"autovacuum_vacuum_threshold", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Minimum number of tuple updates or deletes prior to vacuum."),
                        NULL
                },
                &autovacuum_vac_thresh,
                50, 0, INT_MAX, NULL, NULL
        },
        {
                {"autovacuum_analyze_threshold", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Minimum number of tuple inserts, updates or deletes prior to analyze."),
                        NULL
                },
                &autovacuum_anl_thresh,
                50, 0, INT_MAX, NULL, NULL
        },
        {
                /* see varsup.c for why this is PGC_POSTMASTER not PGC_SIGHUP */
                {"autovacuum_freeze_max_age", PGC_POSTMASTER, AUTOVACUUM,
                        gettext_noop("Age at which to autovacuum a table to prevent transaction ID wraparound."),
                        NULL
                },
                &autovacuum_freeze_max_age,
                200000000, 100000000, 2000000000, NULL, NULL
        },
        {
                /* see max_connections */
                {"autovacuum_max_workers", PGC_POSTMASTER, AUTOVACUUM,
                        gettext_noop("Sets the maximum number of simultaneously running autovacuum worker processes."),
                        NULL
                },
                &autovacuum_max_workers,
                3, 1, INT_MAX / 4, assign_autovacuum_max_workers, NULL
        },

        {
                {"tcp_keepalives_idle", PGC_USERSET, CLIENT_CONN_OTHER,
                        gettext_noop("Time between issuing TCP keepalives."),
                        gettext_noop("A value of 0 uses the system default."),
                        GUC_UNIT_S
                },
                &tcp_keepalives_idle,
                0, 0, INT_MAX, assign_tcp_keepalives_idle, show_tcp_keepalives_idle
        },

        {
                {"tcp_keepalives_interval", PGC_USERSET, CLIENT_CONN_OTHER,
                        gettext_noop("Time between TCP keepalive retransmits."),
                        gettext_noop("A value of 0 uses the system default."),
                        GUC_UNIT_S
                },
                &tcp_keepalives_interval,
                0, 0, INT_MAX, assign_tcp_keepalives_interval, show_tcp_keepalives_interval
        },

        {
                {"tcp_keepalives_count", PGC_USERSET, CLIENT_CONN_OTHER,
                        gettext_noop("Maximum number of TCP keepalive retransmits."),
                        gettext_noop("This controls the number of consecutive keepalive retransmits that can be "
                                                 "lost before a connection is considered dead. A value of 0 uses the "
                                                 "system default."),
                },
                &tcp_keepalives_count,
                0, 0, INT_MAX, assign_tcp_keepalives_count, show_tcp_keepalives_count
        },

        {
                {"gin_fuzzy_search_limit", PGC_USERSET, CLIENT_CONN_OTHER,
                        gettext_noop("Sets the maximum allowed result for exact search by GIN."),
                        NULL,
                        0
                },
                &GinFuzzySearchLimit,
                0, 0, INT_MAX, NULL, NULL
        },

        {
                {"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's assumption about the size of the disk cache."),
                        gettext_noop("That is, the portion of the kernel's disk cache that "
                                                 "will be used for PostgreSQL data files. This is measured in disk "
                                                 "pages, which are normally 8 kB each."),
                        GUC_UNIT_BLOCKS,
                },
                &effective_cache_size,
                DEFAULT_EFFECTIVE_CACHE_SIZE, 1, INT_MAX, NULL, NULL
        },

        {
                /* Can't be set in postgresql.conf */
                {"server_version_num", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the server version as an integer."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &server_version_num,
                PG_VERSION_NUM, PG_VERSION_NUM, PG_VERSION_NUM, NULL, NULL
        },

        {
                {"log_temp_files", PGC_SUSET, LOGGING_WHAT,
                        gettext_noop("Log the use of temporary files larger than this number of kilobytes."),
                        gettext_noop("Zero logs all files. The default is -1 (turning this feature off)."),
                        GUC_UNIT_KB
                },
                &log_temp_files,
                -1, -1, INT_MAX, NULL, NULL
        },

        {
                {"track_activity_query_size", PGC_POSTMASTER, RESOURCES_MEM,
                        gettext_noop("Sets the size reserved for pg_stat_activity.current_query, in bytes."),
                        NULL,
                },
                &pgstat_track_activity_query_size,
                1024, 100, 102400, NULL, NULL
        },

        /* End-of-list marker */
        {
                {NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL
        }
};


static struct config_real ConfigureNamesReal[] =
{
        {
                {"seq_page_cost", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's estimate of the cost of a "
                                                 "sequentially fetched disk page."),
                        NULL
                },
                &seq_page_cost,
                DEFAULT_SEQ_PAGE_COST, 0, DBL_MAX, NULL, NULL
        },
        {
                {"random_page_cost", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's estimate of the cost of a "
                                                 "nonsequentially fetched disk page."),
                        NULL
                },
                &random_page_cost,
                DEFAULT_RANDOM_PAGE_COST, 0, DBL_MAX, NULL, NULL
        },
        {
                {"cpu_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's estimate of the cost of "
                                                 "processing each tuple (row)."),
                        NULL
                },
                &cpu_tuple_cost,
                DEFAULT_CPU_TUPLE_COST, 0, DBL_MAX, NULL, NULL
        },
        {
                {"cpu_index_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's estimate of the cost of "
                                                 "processing each index entry during an index scan."),
                        NULL
                },
                &cpu_index_tuple_cost,
                DEFAULT_CPU_INDEX_TUPLE_COST, 0, DBL_MAX, NULL, NULL
        },
        {
                {"cpu_operator_cost", PGC_USERSET, QUERY_TUNING_COST,
                        gettext_noop("Sets the planner's estimate of the cost of "
                                                 "processing each operator or function call."),
                        NULL
                },
                &cpu_operator_cost,
                DEFAULT_CPU_OPERATOR_COST, 0, DBL_MAX, NULL, NULL
        },

        {
                {"cursor_tuple_fraction", PGC_USERSET, QUERY_TUNING_OTHER,
                        gettext_noop("Sets the planner's estimate of the fraction of "
                                                 "a cursor's rows that will be retrieved."),
                        NULL
                },
                &cursor_tuple_fraction,
                DEFAULT_CURSOR_TUPLE_FRACTION, 0.0, 1.0, NULL, NULL
        },

        {
                {"geqo_selection_bias", PGC_USERSET, QUERY_TUNING_GEQO,
                        gettext_noop("GEQO: selective pressure within the population."),
                        NULL
                },
                &Geqo_selection_bias,
                DEFAULT_GEQO_SELECTION_BIAS, MIN_GEQO_SELECTION_BIAS,
                MAX_GEQO_SELECTION_BIAS, NULL, NULL
        },

        {
                {"bgwriter_lru_multiplier", PGC_SIGHUP, RESOURCES,
                        gettext_noop("Multiple of the average buffer usage to free per round."),
                        NULL
                },
                &bgwriter_lru_multiplier,
                2.0, 0.0, 10.0, NULL, NULL
        },

        {
                {"seed", PGC_USERSET, UNGROUPED,
                        gettext_noop("Sets the seed for random-number generation."),
                        NULL,
                        GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &phony_random_seed,
                0.0, -1.0, 1.0, assign_random_seed, show_random_seed
        },

        {
                {"autovacuum_vacuum_scale_factor", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Number of tuple updates or deletes prior to vacuum as a fraction of reltuples."),
                        NULL
                },
                &autovacuum_vac_scale,
                0.2, 0.0, 100.0, NULL, NULL
        },
        {
                {"autovacuum_analyze_scale_factor", PGC_SIGHUP, AUTOVACUUM,
                        gettext_noop("Number of tuple inserts, updates or deletes prior to analyze as a fraction of reltuples."),
                        NULL
                },
                &autovacuum_anl_scale,
                0.1, 0.0, 100.0, NULL, NULL
        },

        {
                {"checkpoint_completion_target", PGC_SIGHUP, WAL_CHECKPOINTS,
                        gettext_noop("Time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval."),
                        NULL
                },
                &CheckPointCompletionTarget,
                0.5, 0.0, 1.0, NULL, NULL
        },

        /* End-of-list marker */
        {
                {NULL, 0, 0, NULL, NULL}, NULL, 0.0, 0.0, 0.0, NULL, NULL
        }
};


static struct config_string ConfigureNamesString[] =
{
        {
                {"archive_command", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("Sets the shell command that will be called to archive a WAL file."),
                        NULL
                },
                &XLogArchiveCommand,
                "", NULL, show_archive_command
        },

        {
                {"client_encoding", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the client's character set encoding."),
                        NULL,
                        GUC_IS_NAME | GUC_REPORT
                },
                &client_encoding_string,
                "SQL_ASCII", assign_client_encoding, NULL
        },

        {
                {"log_line_prefix", PGC_SIGHUP, LOGGING_WHAT,
                        gettext_noop("Controls information prefixed to each log line."),
                        gettext_noop("If blank, no prefix is used.")
                },
                &Log_line_prefix,
                "", NULL, NULL
        },

        {
                {"log_timezone", PGC_SIGHUP, LOGGING_WHAT,
                        gettext_noop("Sets the time zone to use in log messages."),
                        NULL
                },
                &log_timezone_string,
                "UNKNOWN", assign_log_timezone, show_log_timezone
        },

        {
                {"DateStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the display format for date and time values."),
                        gettext_noop("Also controls interpretation of ambiguous "
                                                 "date inputs."),
                        GUC_LIST_INPUT | GUC_REPORT
                },
                &datestyle_string,
                "ISO, MDY", assign_datestyle, NULL
        },

        {
                {"default_tablespace", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the default tablespace to create tables and indexes in."),
                        gettext_noop("An empty string selects the database's default tablespace."),
                        GUC_IS_NAME
                },
                &default_tablespace,
                "", assign_default_tablespace, NULL
        },

        {
                {"temp_tablespaces", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the tablespace(s) to use for temporary tables and sort files."),
                        NULL,
                        GUC_LIST_INPUT | GUC_LIST_QUOTE
                },
                &temp_tablespaces,
                "", assign_temp_tablespaces, NULL
        },

        {
                {"dynamic_library_path", PGC_SUSET, CLIENT_CONN_OTHER,
                        gettext_noop("Sets the path for dynamically loadable modules."),
                        gettext_noop("If a dynamically loadable module needs to be opened and "
                                                 "the specified name does not have a directory component (i.e., the "
                                                 "name does not contain a slash), the system will search this path for "
                                                 "the specified file."),
                        GUC_SUPERUSER_ONLY
                },
                &Dynamic_library_path,
                "$libdir", NULL, NULL
        },

        {
                {"krb_server_keyfile", PGC_SIGHUP, CONN_AUTH_SECURITY,
                        gettext_noop("Sets the location of the Kerberos server key file."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &pg_krb_server_keyfile,
                PG_KRB_SRVTAB, NULL, NULL
        },

        {
                {"krb_srvname", PGC_SIGHUP, CONN_AUTH_SECURITY,
                        gettext_noop("Sets the name of the Kerberos service."),
                        NULL
                },
                &pg_krb_srvnam,
                PG_KRB_SRVNAM, NULL, NULL
        },

        {
                {"bonjour_name", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the Bonjour broadcast service name."),
                        NULL
                },
                &bonjour_name,
                "", NULL, NULL
        },

        /* See main.c about why defaults for LC_foo are not all alike */

        {
                {"lc_collate", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                        gettext_noop("Shows the collation order locale."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &locale_collate,
                "C", NULL, NULL
        },

        {
                {"lc_ctype", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                        gettext_noop("Shows the character classification and case conversion locale."),
                        NULL,
                        GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &locale_ctype,
                "C", NULL, NULL
        },

        {
                {"lc_messages", PGC_SUSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the language in which messages are displayed."),
                        NULL
                },
                &locale_messages,
                "", locale_messages_assign, NULL
        },

        {
                {"lc_monetary", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the locale for formatting monetary amounts."),
                        NULL
                },
                &locale_monetary,
                "C", locale_monetary_assign, NULL
        },

        {
                {"lc_numeric", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the locale for formatting numbers."),
                        NULL
                },
                &locale_numeric,
                "C", locale_numeric_assign, NULL
        },

        {
                {"lc_time", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the locale for formatting date and time values."),
                        NULL
                },
                &locale_time,
                "C", locale_time_assign, NULL
        },

        {
                {"shared_preload_libraries", PGC_POSTMASTER, RESOURCES_KERNEL,
                        gettext_noop("Lists shared libraries to preload into server."),
                        NULL,
                        GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
                },
                &shared_preload_libraries_string,
                "", NULL, NULL
        },

        {
                {"local_preload_libraries", PGC_BACKEND, CLIENT_CONN_OTHER,
                        gettext_noop("Lists shared libraries to preload into each backend."),
                        NULL,
                        GUC_LIST_INPUT | GUC_LIST_QUOTE
                },
                &local_preload_libraries_string,
                "", NULL, NULL
        },

        {
                {"search_path", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the schema search order for names that are not schema-qualified."),
                        NULL,
                        GUC_LIST_INPUT | GUC_LIST_QUOTE
                },
                &namespace_search_path,
                "\"$user\",public", assign_search_path, NULL
        },

        {
                /* Can't be set in postgresql.conf */
                {"server_encoding", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the server (database) character set encoding."),
                        NULL,
                        GUC_IS_NAME | GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &server_encoding_string,
                "SQL_ASCII", NULL, NULL
        },

        {
                /* Can't be set in postgresql.conf */
                {"server_version", PGC_INTERNAL, PRESET_OPTIONS,
                        gettext_noop("Shows the server version."),
                        NULL,
                        GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &server_version_string,
                PG_VERSION, NULL, NULL
        },

        {
                /* Not for general use --- used by SET ROLE */
                {"role", PGC_USERSET, UNGROUPED,
                        gettext_noop("Sets the current role."),
                        NULL,
                        GUC_IS_NAME | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &role_string,
                "none", assign_role, show_role
        },

        {
                /* Not for general use --- used by SET SESSION AUTHORIZATION */
                {"session_authorization", PGC_USERSET, UNGROUPED,
                        gettext_noop("Sets the session user name."),
                        NULL,
                        GUC_IS_NAME | GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &session_authorization_string,
                NULL, assign_session_authorization, show_session_authorization
        },

        {
                {"log_destination", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Sets the destination for server log output."),
                        gettext_noop("Valid values are combinations of \"stderr\", "
                                                 "\"syslog\", \"csvlog\", and \"eventlog\", "
                                                 "depending on the platform."),
                        GUC_LIST_INPUT
                },
                &log_destination_string,
                "stderr", assign_log_destination, NULL
        },
        {
                {"log_directory", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Sets the destination directory for log files."),
                        gettext_noop("Can be specified as relative to the data directory "
                                                 "or as absolute path."),
                        GUC_SUPERUSER_ONLY
                },
                &Log_directory,
                "pg_log", assign_canonical_path, NULL
        },
        {
                {"log_filename", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Sets the file name pattern for log files."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &Log_filename,
                "postgresql-%Y-%m-%d_%H%M%S.log", NULL, NULL
        },

#ifdef HAVE_SYSLOG
        {
                {"syslog_ident", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Sets the program name used to identify PostgreSQL "
                                                 "messages in syslog."),
                        NULL
                },
                &syslog_ident_str,
                "postgres", assign_syslog_ident, NULL
        },
#endif

        {
                {"TimeZone", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the time zone for displaying and interpreting time stamps."),
                        NULL,
                        GUC_REPORT
                },
                &timezone_string,
                "UNKNOWN", assign_timezone, show_timezone
        },
        {
                {"timezone_abbreviations", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Selects a file of time zone abbreviations."),
                        NULL
                },
                &timezone_abbreviations_string,
                "UNKNOWN", assign_timezone_abbreviations, NULL
        },

        {
                {"transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the current transaction's isolation level."),
                        NULL,
                        GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
                },
                &XactIsoLevel_string,
                NULL, assign_XactIsoLevel, show_XactIsoLevel
        },

        {
                {"unix_socket_group", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the owning group of the Unix-domain socket."),
                        gettext_noop("The owning user of the socket is always the user "
                                                 "that starts the server.")
                },
                &Unix_socket_group,
                "", NULL, NULL
        },

        {
                {"unix_socket_directory", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the directory where the Unix-domain socket will be created."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &UnixSocketDir,
                "", assign_canonical_path, NULL
        },

        {
                {"listen_addresses", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                        gettext_noop("Sets the host name or IP address(es) to listen to."),
                        NULL,
                        GUC_LIST_INPUT
                },
                &ListenAddresses,
                "localhost", NULL, NULL
        },

        {
                {"custom_variable_classes", PGC_SIGHUP, CUSTOM_OPTIONS,
                        gettext_noop("Sets the list of known custom variable classes."),
                        NULL,
                        GUC_LIST_INPUT | GUC_LIST_QUOTE
                },
                &custom_variable_classes,
                NULL, assign_custom_variable_classes, NULL
        },

        {
                {"data_directory", PGC_POSTMASTER, FILE_LOCATIONS,
                        gettext_noop("Sets the server's data directory."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &data_directory,
                NULL, NULL, NULL
        },

        {
                {"config_file", PGC_POSTMASTER, FILE_LOCATIONS,
                        gettext_noop("Sets the server's main configuration file."),
                        NULL,
                        GUC_DISALLOW_IN_FILE | GUC_SUPERUSER_ONLY
                },
                &ConfigFileName,
                NULL, NULL, NULL
        },

        {
                {"hba_file", PGC_POSTMASTER, FILE_LOCATIONS,
                        gettext_noop("Sets the server's \"hba\" configuration file."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &HbaFileName,
                NULL, NULL, NULL
        },

        {
                {"ident_file", PGC_POSTMASTER, FILE_LOCATIONS,
                        gettext_noop("Sets the server's \"ident\" configuration file."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &IdentFileName,
                NULL, NULL, NULL
        },

        {
                {"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
                        gettext_noop("Writes the postmaster PID to the specified file."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &external_pid_file,
                NULL, assign_canonical_path, NULL
        },

        {
                {"stats_temp_directory", PGC_SIGHUP, STATS_COLLECTOR,
                        gettext_noop("Writes temporary statistics files to the specified directory."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &pgstat_temp_directory,
                "pg_stat_tmp", assign_pgstat_temp_directory, NULL
        },

        {
                {"default_text_search_config", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets default text search configuration."),
                        NULL
                },
                &TSCurrentConfig,
                "pg_catalog.simple", assignTSCurrentConfig, NULL
        },

#ifdef USE_SSL
        {
                {"ssl_ciphers", PGC_POSTMASTER, CONN_AUTH_SECURITY,
                        gettext_noop("Sets the list of allowed SSL ciphers."),
                        NULL,
                        GUC_SUPERUSER_ONLY
                },
                &SSLCipherSuites,
                "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH", NULL, NULL
        },
#endif   /* USE_SSL */

        /* End-of-list marker */
        {
                {NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL
        }
};


static struct config_enum ConfigureNamesEnum[] =
{
        {
                {"backslash_quote", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Sets whether \"\\'\" is allowed in string literals."),
                        NULL
                },
                &backslash_quote,
                BACKSLASH_QUOTE_SAFE_ENCODING, backslash_quote_options, NULL, NULL
        },

        {
                {"client_min_messages", PGC_USERSET, LOGGING_WHEN,
                        gettext_noop("Sets the message levels that are sent to the client."),
                        gettext_noop("Each level includes all the levels that follow it. The later"
                                                 " the level, the fewer messages are sent.")
                },
                &client_min_messages,
                NOTICE, client_message_level_options, NULL, NULL
        },

        {
                {"constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
                        gettext_noop("Enables the planner to use constraints to optimize queries."),
                        gettext_noop("Table scans will be skipped if their constraints"
                                                 " guarantee that no rows match the query.")
                },
                &constraint_exclusion,
                CONSTRAINT_EXCLUSION_PARTITION, constraint_exclusion_options,
                NULL, NULL
        },

        {
                {"default_transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the transaction isolation level of each new transaction."),
                        NULL
                },
                &DefaultXactIsoLevel,
                XACT_READ_COMMITTED, isolation_level_options, NULL, NULL
        },

        {
                {"IntervalStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
                        gettext_noop("Sets the display format for interval values."),
                        NULL,
                        GUC_REPORT
                },
                &IntervalStyle,
                INTSTYLE_POSTGRES, intervalstyle_options, NULL, NULL
        },

        {
                {"log_error_verbosity", PGC_SUSET, LOGGING_WHEN,
                        gettext_noop("Sets the verbosity of logged messages."),
                        NULL
                },
                &Log_error_verbosity,
                PGERROR_DEFAULT, log_error_verbosity_options, NULL, NULL
        },

        {
                {"log_min_messages", PGC_SUSET, LOGGING_WHEN,
                        gettext_noop("Sets the message levels that are logged."),
                        gettext_noop("Each level includes all the levels that follow it. The later"
                                                 " the level, the fewer messages are sent.")
                },
                &log_min_messages,
                WARNING, server_message_level_options, NULL, NULL
        },

        {
                {"log_min_error_statement", PGC_SUSET, LOGGING_WHEN,
                        gettext_noop("Causes all statements generating error at or above this level to be logged."),
                        gettext_noop("Each level includes all the levels that follow it. The later"
                                                 " the level, the fewer messages are sent.")
                },
                &log_min_error_statement,
                ERROR, server_message_level_options, NULL, NULL
        },

        {
                {"log_statement", PGC_SUSET, LOGGING_WHAT,
                        gettext_noop("Sets the type of statements logged."),
                        NULL
                },
                &log_statement,
                LOGSTMT_NONE, log_statement_options, NULL, NULL
        },

#ifdef HAVE_SYSLOG
        {
                {"syslog_facility", PGC_SIGHUP, LOGGING_WHERE,
                        gettext_noop("Sets the syslog \"facility\" to be used when syslog enabled."),
                        NULL
                },
                &syslog_facility,
                LOG_LOCAL0, syslog_facility_options, assign_syslog_facility, NULL
        },
#endif

        {
                {"regex_flavor", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Sets the regular expression \"flavor\"."),
                        NULL
                },
                &regex_flavor,
                REG_ADVANCED, regex_flavor_options, NULL, NULL
        },

        {
                {"session_replication_role", PGC_SUSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets the session's behavior for triggers and rewrite rules."),
                        NULL
                },
                &SessionReplicationRole,
                SESSION_REPLICATION_ROLE_ORIGIN, session_replication_role_options,
                assign_session_replication_role, NULL
        },

        {
                {"track_functions", PGC_SUSET, STATS_COLLECTOR,
                        gettext_noop("Collects function-level statistics on database activity."),
                        NULL
                },
                &pgstat_track_functions,
                TRACK_FUNC_OFF, track_function_options, NULL, NULL
        },

        {
                {"wal_sync_method", PGC_SIGHUP, WAL_SETTINGS,
                        gettext_noop("Selects the method used for forcing WAL updates to disk."),
                        NULL
                },
                &sync_method,
                DEFAULT_SYNC_METHOD, sync_method_options, 
                assign_xlog_sync_method, NULL
        },

        {
                {"xmlbinary", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets how binary values are to be encoded in XML."),
                        NULL
                },
                &xmlbinary,
                XMLBINARY_BASE64, xmlbinary_options, NULL, NULL
        },

        {
                {"xmloption", PGC_USERSET, CLIENT_CONN_STATEMENT,
                        gettext_noop("Sets whether XML data in implicit parsing and serialization "
                                                 "operations is to be considered as documents or content fragments."),
                        NULL
                },
                &xmloption,
                XMLOPTION_CONTENT, xmloption_options, NULL, NULL
        },


        /* End-of-list marker */
        {
                {NULL, 0, 0, NULL, NULL}, NULL, 0, NULL, NULL, NULL
        }
};

/******** end of options list ********/


/*
 * To allow continued support of obsolete names for GUC variables, we apply
 * the following mappings to any unrecognized name.  Note that an old name
 * should be mapped to a new one only if the new variable has very similar
 * semantics to the old.
 */
static const char *const map_old_guc_names[] = {
        "sort_mem", "work_mem",
        "vacuum_mem", "maintenance_work_mem",
        NULL
};


/*
 * Actual lookup of variables is done through this single, sorted array.
 */
static struct config_generic **guc_variables;

/* Current number of variables contained in the vector */
static int      num_guc_variables;

/* Vector capacity */
static int      size_guc_variables;


static bool guc_dirty;                  /* TRUE if need to do commit/abort work */

static bool reporting_enabled;  /* TRUE to enable GUC_REPORT */

static int      GUCNestLevel = 0;       /* 1 when in main transaction */


static int      guc_var_compare(const void *a, const void *b);
static int      guc_name_compare(const char *namea, const char *nameb);
static void InitializeOneGUCOption(struct config_generic *gconf);
static void push_old_value(struct config_generic * gconf, GucAction action);
static void ReportGUCOption(struct config_generic * record);
static void ShowGUCConfigOption(const char *name, DestReceiver *dest);
static void ShowAllGUCConfig(DestReceiver *dest);
static char *_ShowOption(struct config_generic * record, bool use_units);
static bool is_newvalue_equal(struct config_generic * record, const char *newvalue);


/*
 * Some infrastructure for checking malloc/strdup/realloc calls
 */
static void *
guc_malloc(int elevel, size_t size)
{
        void       *data;

        data = malloc(size);
        if (data == NULL)
                ereport(elevel,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
        return data;
}

static void *
guc_realloc(int elevel, void *old, size_t size)
{
        void       *data;

        data = realloc(old, size);
        if (data == NULL)
                ereport(elevel,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
        return data;
}

static char *
guc_strdup(int elevel, const char *src)
{
        char       *data;

        data = strdup(src);
        if (data == NULL)
                ereport(elevel,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
        return data;
}


/*
 * Support for assigning to a field of a string GUC item.  Free the prior
 * value if it's not referenced anywhere else in the item (including stacked
 * states).
 */
static void
set_string_field(struct config_string * conf, char **field, char *newval)
{
        char       *oldval = *field;
        GucStack   *stack;

        /* Do the assignment */
        *field = newval;

        /* Exit if any duplicate references, or if old value was NULL anyway */
        if (oldval == NULL ||
                oldval == *(conf->variable) ||
                oldval == conf->reset_val ||
                oldval == conf->boot_val)
                return;
        for (stack = conf->gen.stack; stack; stack = stack->prev)
        {
                if (oldval == stack->prior.stringval ||
                        oldval == stack->masked.stringval)
                        return;
        }

        /* Not used anymore, so free it */
        free(oldval);
}

/*
 * Detect whether strval is referenced anywhere in a GUC string item
 */
static bool
string_field_used(struct config_string * conf, char *strval)
{
        GucStack   *stack;

        if (strval == *(conf->variable) ||
                strval == conf->reset_val ||
                strval == conf->boot_val)
                return true;
        for (stack = conf->gen.stack; stack; stack = stack->prev)
        {
                if (strval == stack->prior.stringval ||
                        strval == stack->masked.stringval)
                        return true;
        }
        return false;
}

/*
 * Support for copying a variable's active value into a stack entry
 */
static void
set_stack_value(struct config_generic * gconf, union config_var_value * val)
{
        switch (gconf->vartype)
        {
                case PGC_BOOL:
                        val->boolval =
                                *((struct config_bool *) gconf)->variable;
                        break;
                case PGC_INT:
                        val->intval =
                                *((struct config_int *) gconf)->variable;
                        break;
                case PGC_REAL:
                        val->realval =
                                *((struct config_real *) gconf)->variable;
                        break;
                case PGC_STRING:
                        /* we assume stringval is NULL if not valid */
                        set_string_field((struct config_string *) gconf,
                                                         &(val->stringval),
                                                         *((struct config_string *) gconf)->variable);
                        break;
                case PGC_ENUM:
                        val->enumval = 
                                *((struct config_enum *) gconf)->variable;
                        break;
        }
}

/*
 * Support for discarding a no-longer-needed value in a stack entry
 */
static void
discard_stack_value(struct config_generic * gconf, union config_var_value * val)
{
        switch (gconf->vartype)
        {
                case PGC_BOOL:
                case PGC_INT:
                case PGC_REAL:
                case PGC_ENUM:
                        /* no need to do anything */
                        break;
                case PGC_STRING:
                        set_string_field((struct config_string *) gconf,
                                                         &(val->stringval),
                                                         NULL);
                        break;
        }
}


/*
 * Fetch the sorted array pointer (exported for help_config.c's use ONLY)
 */
struct config_generic **
get_guc_variables(void)
{
        return guc_variables;
}


/*
 * Build the sorted array.      This is split out so that it could be
 * re-executed after startup (eg, we could allow loadable modules to
 * add vars, and then we'd need to re-sort).
 */
void
build_guc_variables(void)
{
        int                     size_vars;
        int                     num_vars = 0;
        struct config_generic **guc_vars;
        int                     i;

        for (i = 0; ConfigureNamesBool[i].gen.name; i++)
        {
                struct config_bool *conf = &ConfigureNamesBool[i];

                /* Rather than requiring vartype to be filled in by hand, do this: */
                conf->gen.vartype = PGC_BOOL;
                num_vars++;
        }

        for (i = 0; ConfigureNamesInt[i].gen.name; i++)
        {
                struct config_int *conf = &ConfigureNamesInt[i];

                conf->gen.vartype = PGC_INT;
                num_vars++;
        }

        for (i = 0; ConfigureNamesReal[i].gen.name; i++)
        {
                struct config_real *conf = &ConfigureNamesReal[i];

                conf->gen.vartype = PGC_REAL;
                num_vars++;
        }

        for (i = 0; ConfigureNamesString[i].gen.name; i++)
        {
                struct config_string *conf = &ConfigureNamesString[i];

                conf->gen.vartype = PGC_STRING;
                num_vars++;
        }

        for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
        {
                struct config_enum *conf = &ConfigureNamesEnum[i];

                conf->gen.vartype = PGC_ENUM;
                num_vars++;
        }

        /*
         * Create table with 20% slack
         */
        size_vars = num_vars + num_vars / 4;

        guc_vars = (struct config_generic **)
                guc_malloc(FATAL, size_vars * sizeof(struct config_generic *));

        num_vars = 0;

        for (i = 0; ConfigureNamesBool[i].gen.name; i++)
                guc_vars[num_vars++] = &ConfigureNamesBool[i].gen;

        for (i = 0; ConfigureNamesInt[i].gen.name; i++)
                guc_vars[num_vars++] = &ConfigureNamesInt[i].gen;

        for (i = 0; ConfigureNamesReal[i].gen.name; i++)
                guc_vars[num_vars++] = &ConfigureNamesReal[i].gen;

        for (i = 0; ConfigureNamesString[i].gen.name; i++)
                guc_vars[num_vars++] = &ConfigureNamesString[i].gen;

        for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
                guc_vars[num_vars++] = &ConfigureNamesEnum[i].gen;

        if (guc_variables)
                free(guc_variables);
        guc_variables = guc_vars;
        num_guc_variables = num_vars;
        size_guc_variables = size_vars;
        qsort((void *) guc_variables, num_guc_variables,
                  sizeof(struct config_generic *), guc_var_compare);
}

/*
 * Add a new GUC variable to the list of known variables. The
 * list is expanded if needed.
 */
static bool
add_guc_variable(struct config_generic * var, int elevel)
{
        if (num_guc_variables + 1 >= size_guc_variables)
        {
                /*
                 * Increase the vector by 25%
                 */
                int                     size_vars = size_guc_variables + size_guc_variables / 4;
                struct config_generic **guc_vars;

                if (size_vars == 0)
                {
                        size_vars = 100;
                        guc_vars = (struct config_generic **)
                                guc_malloc(elevel, size_vars * sizeof(struct config_generic *));
                }
                else
                {
                        guc_vars = (struct config_generic **)
                                guc_realloc(elevel, guc_variables, size_vars * sizeof(struct config_generic *));
                }

                if (guc_vars == NULL)
                        return false;           /* out of memory */

                guc_variables = guc_vars;
                size_guc_variables = size_vars;
        }
        guc_variables[num_guc_variables++] = var;
        qsort((void *) guc_variables, num_guc_variables,
                  sizeof(struct config_generic *), guc_var_compare);
        return true;
}

/*
 * Create and add a placeholder variable. It's presumed to belong
 * to a valid custom variable class at this point.
 */
static struct config_generic *
add_placeholder_variable(const char *name, int elevel)
{
        size_t          sz = sizeof(struct config_string) + sizeof(char *);
        struct config_string *var;
        struct config_generic *gen;

        var = (struct config_string *) guc_malloc(elevel, sz);
        if (var == NULL)
                return NULL;
        memset(var, 0, sz);
        gen = &var->gen;

        gen->name = guc_strdup(elevel, name);
        if (gen->name == NULL)
        {
                free(var);
                return NULL;
        }

        gen->context = PGC_USERSET;
        gen->group = CUSTOM_OPTIONS;
        gen->short_desc = "GUC placeholder variable";
        gen->flags = GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_CUSTOM_PLACEHOLDER;
        gen->vartype = PGC_STRING;

        /*
         * The char* is allocated at the end of the struct since we have no
         * 'static' place to point to.  Note that the current value, as well as
         * the boot and reset values, start out NULL.
         */
        var->variable = (char **) (var + 1);

        if (!add_guc_variable((struct config_generic *) var, elevel))
        {
                free((void *) gen->name);
                free(var);
                return NULL;
        }

        return gen;
}

/*
 * Detect whether the portion of "name" before dotPos matches any custom
 * variable class name listed in custom_var_classes.  The latter must be
 * formatted the way that assign_custom_variable_classes does it, ie,
 * no whitespace.  NULL is valid for custom_var_classes.
 */
static bool
is_custom_class(const char *name, int dotPos, const char *custom_var_classes)
{
        bool            result = false;
        const char *ccs = custom_var_classes;

        if (ccs != NULL)
        {
                const char *start = ccs;

                for (;; ++ccs)
                {
                        char            c = *ccs;

                        if (c == '\0' || c == ',')
                        {
                                if (dotPos == ccs - start && strncmp(start, name, dotPos) == 0)
                                {
                                        result = true;
                                        break;
                                }
                                if (c == '\0')
                                        break;
                                start = ccs + 1;
                        }
                }
        }
        return result;
}

/*
 * Look up option NAME.  If it exists, return a pointer to its record,
 * else return NULL.  If create_placeholders is TRUE, we'll create a
 * placeholder record for a valid-looking custom variable name.
 */
static struct config_generic *
find_option(const char *name, bool create_placeholders, int elevel)
{
        const char **key = &name;
        struct config_generic **res;
        int                     i;

        Assert(name);

        /*
         * By equating const char ** with struct config_generic *, we are assuming
         * the name field is first in config_generic.
         */
        res = (struct config_generic **) bsearch((void *) &key,
                                                                                         (void *) guc_variables,
                                                                                         num_guc_variables,
                                                                                         sizeof(struct config_generic *),
                                                                                         guc_var_compare);
        if (res)
                return *res;

        /*
         * See if the name is an obsolete name for a variable.  We assume that the
         * set of supported old names is short enough that a brute-force search is
         * the best way.
         */
        for (i = 0; map_old_guc_names[i] != NULL; i += 2)
        {
                if (guc_name_compare(name, map_old_guc_names[i]) == 0)
                        return find_option(map_old_guc_names[i + 1], false, elevel);
        }

        if (create_placeholders)
        {
                /*
                 * Check if the name is qualified, and if so, check if the qualifier
                 * matches any custom variable class.  If so, add a placeholder.
                 */
                const char *dot = strchr(name, GUC_QUALIFIER_SEPARATOR);

                if (dot != NULL &&
                        is_custom_class(name, dot - name, custom_variable_classes))
                        return add_placeholder_variable(name, elevel);
        }

        /* Unknown name */
        return NULL;
}


/*
 * comparator for qsorting and bsearching guc_variables array
 */
static int
guc_var_compare(const void *a, const void *b)
{
        struct config_generic *confa = *(struct config_generic **) a;
        struct config_generic *confb = *(struct config_generic **) b;

        return guc_name_compare(confa->name, confb->name);
}

/*
 * the bare comparison function for GUC names
 */
static int
guc_name_compare(const char *namea, const char *nameb)
{
        /*
         * The temptation to use strcasecmp() here must be resisted, because the
         * array ordering has to remain stable across setlocale() calls. So, build
         * our own with a simple ASCII-only downcasing.
         */
        while (*namea && *nameb)
        {
                char            cha = *namea++;
                char            chb = *nameb++;

                if (cha >= 'A' && cha <= 'Z')
                        cha += 'a' - 'A';
                if (chb >= 'A' && chb <= 'Z')
                        chb += 'a' - 'A';
                if (cha != chb)
                        return cha - chb;
        }
        if (*namea)
                return 1;                               /* a is longer */
        if (*nameb)
                return -1;                              /* b is longer */
        return 0;
}


/*
 * Initialize GUC options during program startup.
 *
 * Note that we cannot read the config file yet, since we have not yet
 * processed command-line switches.
 */
void
InitializeGUCOptions(void)
{
        int                     i;
        char       *env;
        long            stack_rlimit;

        /*
         * Before log_line_prefix could possibly receive a nonempty setting, make
         * sure that timezone processing is minimally alive (see elog.c).
         */
        pg_timezone_pre_initialize();

        /*
         * Build sorted array of all GUC variables.
         */
        build_guc_variables();

        /*
         * Load all variables with their compiled-in defaults, and initialize
         * status fields as needed.
         */
        for (i = 0; i < num_guc_variables; i++)
        {
                InitializeOneGUCOption(guc_variables[i]);
        }

        guc_dirty = false;

        reporting_enabled = false;

        /*
         * Prevent any attempt to override the transaction modes from
         * non-interactive sources.
         */
        SetConfigOption("transaction_isolation", "default",
                                        PGC_POSTMASTER, PGC_S_OVERRIDE);
        SetConfigOption("transaction_read_only", "no",
                                        PGC_POSTMASTER, PGC_S_OVERRIDE);

        /*
         * For historical reasons, some GUC parameters can receive defaults from
         * environment variables.  Process those settings.      NB: if you add or
         * remove anything here, see also ProcessConfigFile().
         */

        env = getenv("PGPORT");
        if (env != NULL)
                SetConfigOption("port", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

        env = getenv("PGDATESTYLE");
        if (env != NULL)
                SetConfigOption("datestyle", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

        env = getenv("PGCLIENTENCODING");
        if (env != NULL)
                SetConfigOption("client_encoding", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

        /*
         * rlimit isn't exactly an "environment variable", but it behaves about
         * the same.  If we can identify the platform stack depth rlimit, increase
         * default stack depth setting up to whatever is safe (but at most 2MB).
         */
        stack_rlimit = get_stack_depth_rlimit();
        if (stack_rlimit > 0)
        {
                int                     new_limit = (stack_rlimit - STACK_DEPTH_SLOP) / 1024L;

                if (new_limit > 100)
                {
                        char            limbuf[16];

                        new_limit = Min(new_limit, 2048);
                        sprintf(limbuf, "%d", new_limit);
                        SetConfigOption("max_stack_depth", limbuf,
                                                        PGC_POSTMASTER, PGC_S_ENV_VAR);
                }
        }
}

/*
 * Initialize one GUC option variable to its compiled-in default.
 */
static void
InitializeOneGUCOption(struct config_generic *gconf)
{
        gconf->status = 0;
        gconf->reset_source = PGC_S_DEFAULT;
        gconf->source = PGC_S_DEFAULT;
        gconf->stack = NULL;
        gconf->sourcefile = NULL;
        gconf->sourceline = 0;

        switch (gconf->vartype)
        {
                case PGC_BOOL:
                {
                        struct config_bool *conf = (struct config_bool *) gconf;

                        if (conf->assign_hook)
                                if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                                   PGC_S_DEFAULT))
                                        elog(FATAL, "failed to initialize %s to %d",
                                                 conf->gen.name, (int) conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                }
                case PGC_INT:
                {
                        struct config_int *conf = (struct config_int *) gconf;

                        Assert(conf->boot_val >= conf->min);
                        Assert(conf->boot_val <= conf->max);
                        if (conf->assign_hook)
                                if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                                   PGC_S_DEFAULT))
                                        elog(FATAL, "failed to initialize %s to %d",
                                                 conf->gen.name, conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                }
                case PGC_REAL:
                {
                        struct config_real *conf = (struct config_real *) gconf;

                        Assert(conf->boot_val >= conf->min);
                        Assert(conf->boot_val <= conf->max);
                        if (conf->assign_hook)
                                if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                                   PGC_S_DEFAULT))
                                        elog(FATAL, "failed to initialize %s to %g",
                                                 conf->gen.name, conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                }
                case PGC_STRING:
                {
                        struct config_string *conf = (struct config_string *) gconf;
                        char       *str;

                        *conf->variable = NULL;
                        conf->reset_val = NULL;

                        if (conf->boot_val == NULL)
                        {
                                /* leave the value NULL, do not call assign hook */
                                break;
                        }

                        str = guc_strdup(FATAL, conf->boot_val);
                        conf->reset_val = str;

                        if (conf->assign_hook)
                        {
                                const char *newstr;

                                newstr = (*conf->assign_hook) (str, true,
                                                                                           PGC_S_DEFAULT);
                                if (newstr == NULL)
                                {
                                        elog(FATAL, "failed to initialize %s to \"%s\"",
                                                 conf->gen.name, str);
                                }
                                else if (newstr != str)
                                {
                                        free(str);

                                        /*
                                         * See notes in set_config_option about casting
                                         */
                                        str = (char *) newstr;
                                        conf->reset_val = str;
                                }
                        }
                        *conf->variable = str;
                        break;
                }
                case PGC_ENUM:
                {
                        struct config_enum *conf = (struct config_enum *) gconf;

                        if (conf->assign_hook)
                                if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                                   PGC_S_DEFAULT))
                                        elog(FATAL, "failed to initialize %s to %s",
                                                 conf->gen.name, 
                                                 config_enum_lookup_by_value(conf, conf->boot_val));
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                }
        }
}


/*
 * Select the configuration files and data directory to be used, and
 * do the initial read of postgresql.conf.
 *
 * This is called after processing command-line switches.
 *              userDoption is the -D switch value if any (NULL if unspecified).
 *              progname is just for use in error messages.
 *
 * Returns true on success; on failure, prints a suitable error message
 * to stderr and returns false.
 */
bool
SelectConfigFiles(const char *userDoption, const char *progname)
{
        char       *configdir;
        char       *fname;
        struct stat stat_buf;

        /* configdir is -D option, or $PGDATA if no -D */
        if (userDoption)
                configdir = make_absolute_path(userDoption);
        else
                configdir = make_absolute_path(getenv("PGDATA"));

        /*
         * Find the configuration file: if config_file was specified on the
         * command line, use it, else use configdir/postgresql.conf.  In any case
         * ensure the result is an absolute path, so that it will be interpreted
         * the same way by future backends.
         */
        if (ConfigFileName)
                fname = make_absolute_path(ConfigFileName);
        else if (configdir)
        {
                fname = guc_malloc(FATAL,
                                                   strlen(configdir) + strlen(CONFIG_FILENAME) + 2);
                sprintf(fname, "%s/%s", configdir, CONFIG_FILENAME);
        }
        else
        {
                write_stderr("%s does not know where to find the server configuration file.\n"
                                         "You must specify the --config-file or -D invocation "
                                         "option or set the PGDATA environment variable.\n",
                                         progname);
                return false;
        }

        /*
         * Set the ConfigFileName GUC variable to its final value, ensuring that
         * it can't be overridden later.
         */
        SetConfigOption("config_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
        free(fname);

        /*
         * Now read the config file for the first time.
         */
        if (stat(ConfigFileName, &stat_buf) != 0)
        {
                write_stderr("%s cannot access the server configuration file \"%s\": %s\n",
                                         progname, ConfigFileName, strerror(errno));
                return false;
        }

        ProcessConfigFile(PGC_POSTMASTER);

        /*
         * If the data_directory GUC variable has been set, use that as DataDir;
         * otherwise use configdir if set; else punt.
         *
         * Note: SetDataDir will copy and absolute-ize its argument, so we don't
         * have to.
         */
        if (data_directory)
                SetDataDir(data_directory);
        else if (configdir)
                SetDataDir(configdir);
        else
        {
                write_stderr("%s does not know where to find the database system data.\n"
                                         "This can be specified as \"data_directory\" in \"%s\", "
                                         "or by the -D invocation option, or by the "
                                         "PGDATA environment variable.\n",
                                         progname, ConfigFileName);
                return false;
        }

        /*
         * Reflect the final DataDir value back into the data_directory GUC var.
         * (If you are wondering why we don't just make them a single variable,
         * it's because the EXEC_BACKEND case needs DataDir to be transmitted to
         * child backends specially.  XXX is that still true?  Given that we now
         * chdir to DataDir, EXEC_BACKEND can read the config file without knowing
         * DataDir in advance.)
         */
        SetConfigOption("data_directory", DataDir, PGC_POSTMASTER, PGC_S_OVERRIDE);

        /*
         * Figure out where pg_hba.conf is, and make sure the path is absolute.
         */
        if (HbaFileName)
                fname = make_absolute_path(HbaFileName);
        else if (configdir)
        {
                fname = guc_malloc(FATAL,
                                                   strlen(configdir) + strlen(HBA_FILENAME) + 2);
                sprintf(fname, "%s/%s", configdir, HBA_FILENAME);
        }
        else
        {
                write_stderr("%s does not know where to find the \"hba\" configuration file.\n"
                                         "This can be specified as \"hba_file\" in \"%s\", "
                                         "or by the -D invocation option, or by the "
                                         "PGDATA environment variable.\n",
                                         progname, ConfigFileName);
                return false;
        }
        SetConfigOption("hba_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
        free(fname);

        /*
         * Likewise for pg_ident.conf.
         */
        if (IdentFileName)
                fname = make_absolute_path(IdentFileName);
        else if (configdir)
        {
                fname = guc_malloc(FATAL,
                                                   strlen(configdir) + strlen(IDENT_FILENAME) + 2);
                sprintf(fname, "%s/%s", configdir, IDENT_FILENAME);
        }
        else
        {
                write_stderr("%s does not know where to find the \"ident\" configuration file.\n"
                                         "This can be specified as \"ident_file\" in \"%s\", "
                                         "or by the -D invocation option, or by the "
                                         "PGDATA environment variable.\n",
                                         progname, ConfigFileName);
                return false;
        }
        SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
        free(fname);

        free(configdir);

        return true;
}


/*
 * Reset all options to their saved default values (implements RESET ALL)
 */
void
ResetAllOptions(void)
{
        int                     i;

        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *gconf = guc_variables[i];

                /* Don't reset non-SET-able values */
                if (gconf->context != PGC_SUSET &&
                        gconf->context != PGC_USERSET)
                        continue;
                /* Don't reset if special exclusion from RESET ALL */
                if (gconf->flags & GUC_NO_RESET_ALL)
                        continue;
                /* No need to reset if wasn't SET */
                if (gconf->source <= PGC_S_OVERRIDE)
                        continue;

                /* Save old value to support transaction abort */
                push_old_value(gconf, GUC_ACTION_SET);

                switch (gconf->vartype)
                {
                        case PGC_BOOL:
                                {
                                        struct config_bool *conf = (struct config_bool *) gconf;

                                        if (conf->assign_hook)
                                                if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                                                   PGC_S_SESSION))
                                                        elog(ERROR, "failed to reset %s", conf->gen.name);
                                        *conf->variable = conf->reset_val;
                                        break;
                                }
                        case PGC_INT:
                                {
                                        struct config_int *conf = (struct config_int *) gconf;

                                        if (conf->assign_hook)
                                                if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                                                   PGC_S_SESSION))
                                                        elog(ERROR, "failed to reset %s", conf->gen.name);
                                        *conf->variable = conf->reset_val;
                                        break;
                                }
                        case PGC_REAL:
                                {
                                        struct config_real *conf = (struct config_real *) gconf;

                                        if (conf->assign_hook)
                                                if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                                                   PGC_S_SESSION))
                                                        elog(ERROR, "failed to reset %s", conf->gen.name);
                                        *conf->variable = conf->reset_val;
                                        break;
                                }
                        case PGC_STRING:
                                {
                                        struct config_string *conf = (struct config_string *) gconf;
                                        char       *str;

                                        /* We need not strdup here */
                                        str = conf->reset_val;

                                        if (conf->assign_hook && str)
                                        {
                                                const char *newstr;

                                                newstr = (*conf->assign_hook) (str, true,
                                                                                                           PGC_S_SESSION);
                                                if (newstr == NULL)
                                                        elog(ERROR, "failed to reset %s", conf->gen.name);
                                                else if (newstr != str)
                                                {
                                                        /*
                                                         * See notes in set_config_option about casting
                                                         */
                                                        str = (char *) newstr;
                                                }
                                        }

                                        set_string_field(conf, conf->variable, str);
                                        break;
                                }
                        case PGC_ENUM:
                                {
                                        struct config_enum *conf = (struct config_enum *) gconf;

                                        if (conf->assign_hook)
                                                if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                                                   PGC_S_SESSION))
                                                        elog(ERROR, "failed to reset %s", conf->gen.name);
                                        *conf->variable = conf->reset_val;
                                        break;
                                }
                }

                gconf->source = gconf->reset_source;

                if (gconf->flags & GUC_REPORT)
                        ReportGUCOption(gconf);
        }
}


/*
 * push_old_value
 *              Push previous state during transactional assignment to a GUC variable.
 */
static void
push_old_value(struct config_generic * gconf, GucAction action)
{
        GucStack   *stack;

        /* If we're not inside a nest level, do nothing */
        if (GUCNestLevel == 0)
                return;

        /* Do we already have a stack entry of the current nest level? */
        stack = gconf->stack;
        if (stack && stack->nest_level >= GUCNestLevel)
        {
                /* Yes, so adjust its state if necessary */
                Assert(stack->nest_level == GUCNestLevel);
                switch (action)
                {
                        case GUC_ACTION_SET:
                                /* SET overrides any prior action at same nest level */
                                if (stack->state == GUC_SET_LOCAL)
                                {
                                        /* must discard old masked value */
                                        discard_stack_value(gconf, &stack->masked);
                                }
                                stack->state = GUC_SET;
                                break;
                        case GUC_ACTION_LOCAL:
                                if (stack->state == GUC_SET)
                                {
                                        /* SET followed by SET LOCAL, remember SET's value */
                                        set_stack_value(gconf, &stack->masked);
                                        stack->state = GUC_SET_LOCAL;
                                }
                                /* in all other cases, no change to stack entry */
                                break;
                        case GUC_ACTION_SAVE:
                                /* Could only have a prior SAVE of same variable */
                                Assert(stack->state == GUC_SAVE);
                                break;
                }
                Assert(guc_dirty);              /* must be set already */
                return;
        }

        /*
         * Push a new stack entry
         *
         * We keep all the stack entries in TopTransactionContext for simplicity.
         */
        stack = (GucStack *) MemoryContextAllocZero(TopTransactionContext,
                                                                                                sizeof(GucStack));

        stack->prev = gconf->stack;
        stack->nest_level = GUCNestLevel;
        switch (action)
        {
                case GUC_ACTION_SET:
                        stack->state = GUC_SET;
                        break;
                case GUC_ACTION_LOCAL:
                        stack->state = GUC_LOCAL;
                        break;
                case GUC_ACTION_SAVE:
                        stack->state = GUC_SAVE;
                        break;
        }
        stack->source = gconf->source;
        set_stack_value(gconf, &stack->prior);

        gconf->stack = stack;

        /* Ensure we remember to pop at end of xact */
        guc_dirty = true;
}


/*
 * Do GUC processing at main transaction start.
 */
void
AtStart_GUC(void)
{
        /*
         * The nest level should be 0 between transactions; if it isn't, somebody
         * didn't call AtEOXact_GUC, or called it with the wrong nestLevel.  We
         * throw a warning but make no other effort to clean up.
         */
        if (GUCNestLevel != 0)
                elog(WARNING, "GUC nest level = %d at transaction start",
                         GUCNestLevel);
        GUCNestLevel = 1;
}

/*
 * Enter a new nesting level for GUC values.  This is called at subtransaction
 * start and when entering a function that has proconfig settings.      NOTE that
 * we must not risk error here, else subtransaction start will be unhappy.
 */
int
NewGUCNestLevel(void)
{
        return ++GUCNestLevel;
}

/*
 * Do GUC processing at transaction or subtransaction commit or abort, or
 * when exiting a function that has proconfig settings.  (The name is thus
 * a bit of a misnomer; perhaps it should be ExitGUCNestLevel or some such.)
 * During abort, we discard all GUC settings that were applied at nesting
 * levels >= nestLevel.  nestLevel == 1 corresponds to the main transaction.
 */
void
AtEOXact_GUC(bool isCommit, int nestLevel)
{
        bool            still_dirty;
        int                     i;

        Assert(nestLevel > 0 && nestLevel <= GUCNestLevel);

        /* Quick exit if nothing's changed in this transaction */
        if (!guc_dirty)
        {
                GUCNestLevel = nestLevel - 1;
                return;
        }

        still_dirty = false;
        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *gconf = guc_variables[i];
                GucStack   *stack;

                /*
                 * Process and pop each stack entry within the nest level.      To
                 * simplify fmgr_security_definer(), we allow failure exit from a
                 * function-with-SET-options to be recovered at the surrounding
                 * transaction or subtransaction abort; so there could be more than
                 * one stack entry to pop.
                 */
                while ((stack = gconf->stack) != NULL &&
                           stack->nest_level >= nestLevel)
                {
                        GucStack   *prev = stack->prev;
                        bool            restorePrior = false;
                        bool            restoreMasked = false;
                        bool            changed;

                        /*
                         * In this next bit, if we don't set either restorePrior or
                         * restoreMasked, we must "discard" any unwanted fields of the
                         * stack entries to avoid leaking memory.  If we do set one of
                         * those flags, unused fields will be cleaned up after restoring.
                         */
                        if (!isCommit)          /* if abort, always restore prior value */
                                restorePrior = true;
                        else if (stack->state == GUC_SAVE)
                                restorePrior = true;
                        else if (stack->nest_level == 1)
                        {
                                /* transaction commit */
                                if (stack->state == GUC_SET_LOCAL)
                                        restoreMasked = true;
                                else if (stack->state == GUC_SET)
                                {
                                        /* we keep the current active value */
                                        discard_stack_value(gconf, &stack->prior);
                                }
                                else    /* must be GUC_LOCAL */
                                        restorePrior = true;
                        }
                        else if (prev == NULL ||
                                         prev->nest_level < stack->nest_level - 1)
                        {
                                /* decrement entry's level and do not pop it */
                                stack->nest_level--;
                                continue;
                        }
                        else
                        {
                                /*
                                 * We have to merge this stack entry into prev. See README for
                                 * discussion of this bit.
                                 */
                                switch (stack->state)
                                {
                                        case GUC_SAVE:
                                                Assert(false);  /* can't get here */

                                        case GUC_SET:
                                                /* next level always becomes SET */
                                                discard_stack_value(gconf, &stack->prior);
                                                if (prev->state == GUC_SET_LOCAL)
                                                        discard_stack_value(gconf, &prev->masked);
                                                prev->state = GUC_SET;
                                                break;

                                        case GUC_LOCAL:
                                                if (prev->state == GUC_SET)
                                                {
                                                        /* LOCAL migrates down */
                                                        prev->masked = stack->prior;
                                                        prev->state = GUC_SET_LOCAL;
                                                }
                                                else
                                                {
                                                        /* else just forget this stack level */
                                                        discard_stack_value(gconf, &stack->prior);
                                                }
                                                break;

                                        case GUC_SET_LOCAL:
                                                /* prior state at this level no longer wanted */
                                                discard_stack_value(gconf, &stack->prior);
                                                /* copy down the masked state */
                                                if (prev->state == GUC_SET_LOCAL)
                                                        discard_stack_value(gconf, &prev->masked);
                                                prev->masked = stack->masked;
                                                prev->state = GUC_SET_LOCAL;
                                                break;
                                }
                        }

                        changed = false;

                        if (restorePrior || restoreMasked)
                        {
                                /* Perform appropriate restoration of the stacked value */
                                union config_var_value newvalue;
                                GucSource       newsource;

                                if (restoreMasked)
                                {
                                        newvalue = stack->masked;
                                        newsource = PGC_S_SESSION;
                                }
                                else
                                {
                                        newvalue = stack->prior;
                                        newsource = stack->source;
                                }

                                switch (gconf->vartype)
                                {
                                        case PGC_BOOL:
                                                {
                                                        struct config_bool *conf = (struct config_bool *) gconf;
                                                        bool            newval = newvalue.boolval;

                                                        if (*conf->variable != newval)
                                                        {
                                                                if (conf->assign_hook)
                                                                        if (!(*conf->assign_hook) (newval,
                                                                                                           true, PGC_S_OVERRIDE))
                                                                                elog(LOG, "failed to commit %s",
                                                                                         conf->gen.name);
                                                                *conf->variable = newval;
                                                                changed = true;
                                                        }
                                                        break;
                                                }
                                        case PGC_INT:
                                                {
                                                        struct config_int *conf = (struct config_int *) gconf;
                                                        int                     newval = newvalue.intval;

                                                        if (*conf->variable != newval)
                                                        {
                                                                if (conf->assign_hook)
                                                                        if (!(*conf->assign_hook) (newval,
                                                                                                           true, PGC_S_OVERRIDE))
                                                                                elog(LOG, "failed to commit %s",
                                                                                         conf->gen.name);
                                                                *conf->variable = newval;
                                                                changed = true;
                                                        }
                                                        break;
                                                }
                                        case PGC_REAL:
                                                {
                                                        struct config_real *conf = (struct config_real *) gconf;
                                                        double          newval = newvalue.realval;

                                                        if (*conf->variable != newval)
                                                        {
                                                                if (conf->assign_hook)
                                                                        if (!(*conf->assign_hook) (newval,
                                                                                                           true, PGC_S_OVERRIDE))
                                                                                elog(LOG, "failed to commit %s",
                                                                                         conf->gen.name);
                                                                *conf->variable = newval;
                                                                changed = true;
                                                        }
                                                        break;
                                                }
                                        case PGC_STRING:
                                                {
                                                        struct config_string *conf = (struct config_string *) gconf;
                                                        char       *newval = newvalue.stringval;

                                                        if (*conf->variable != newval)
                                                        {
                                                                if (conf->assign_hook && newval)
                                                                {
                                                                        const char *newstr;

                                                                        newstr = (*conf->assign_hook) (newval, true,
                                                                                                                         PGC_S_OVERRIDE);
                                                                        if (newstr == NULL)
                                                                                elog(LOG, "failed to commit %s",
                                                                                         conf->gen.name);
                                                                        else if (newstr != newval)
                                                                        {
                                                                                /*
                                                                                 * If newval should now be freed,
                                                                                 * it'll be taken care of below.
                                                                                 *
                                                                                 * See notes in set_config_option
                                                                                 * about casting
                                                                                 */
                                                                                newval = (char *) newstr;
                                                                        }
                                                                }

                                                                set_string_field(conf, conf->variable, newval);
                                                                changed = true;
                                                        }

                                                        /*
                                                         * Release stacked values if not used anymore. We
                                                         * could use discard_stack_value() here, but since
                                                         * we have type-specific code anyway, might as
                                                         * well inline it.
                                                         */
                                                        set_string_field(conf, &stack->prior.stringval, NULL);
                                                        set_string_field(conf, &stack->masked.stringval, NULL);
                                                        break;
                                                }
                                        case PGC_ENUM:
                                                {
                                                        struct config_enum *conf = (struct config_enum *) gconf;
                                                        int newval = newvalue.enumval;

                                                        if (*conf->variable != newval)
                                                        {
                                                                if (conf->assign_hook)
                                                                        if (!(*conf->assign_hook) (newval,
                                                                                                                           true, PGC_S_OVERRIDE))
                                                                                elog(LOG, "failed to commit %s",
                                                                                         conf->gen.name);
                                                                *conf->variable = newval;
                                                                changed = true;
                                                        }
                                                        break;
                                                }
                                }

                                gconf->source = newsource;
                        }

                        /* Finish popping the state stack */
                        gconf->stack = prev;
                        pfree(stack);

                        /* Report new value if we changed it */
                        if (changed && (gconf->flags & GUC_REPORT))
                                ReportGUCOption(gconf);
                }                                               /* end of stack-popping loop */

                if (stack != NULL)
                        still_dirty = true;
        }

        /* If there are no remaining stack entries, we can reset guc_dirty */
        guc_dirty = still_dirty;

        /* Update nesting level */
        GUCNestLevel = nestLevel - 1;
}


/*
 * Start up automatic reporting of changes to variables marked GUC_REPORT.
 * This is executed at completion of backend startup.
 */
void
BeginReportingGUCOptions(void)
{
        int                     i;

        /*
         * Don't do anything unless talking to an interactive frontend of protocol
         * 3.0 or later.
         */
        if (whereToSendOutput != DestRemote ||
                PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
                return;

        reporting_enabled = true;

        /* Transmit initial values of interesting variables */
        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *conf = guc_variables[i];

                if (conf->flags & GUC_REPORT)
                        ReportGUCOption(conf);
        }
}

/*
 * ReportGUCOption: if appropriate, transmit option value to frontend
 */
static void
ReportGUCOption(struct config_generic * record)
{
        if (reporting_enabled && (record->flags & GUC_REPORT))
        {
                char       *val = _ShowOption(record, false);
                StringInfoData msgbuf;

                pq_beginmessage(&msgbuf, 'S');
                pq_sendstring(&msgbuf, record->name);
                pq_sendstring(&msgbuf, val);
                pq_endmessage(&msgbuf);

                pfree(val);
        }
}


/*
 * Try to interpret value as boolean value.  Valid values are: true,
 * false, yes, no, on, off, 1, 0; as well as unique prefixes thereof.
 * If the string parses okay, return true, else false.
 * If okay and result is not NULL, return the value in *result.
 */
bool
parse_bool(const char *value, bool *result)
{
        size_t          len = strlen(value);

        if (pg_strncasecmp(value, "true", len) == 0)
        {
                if (result)
                        *result = true;
        }
        else if (pg_strncasecmp(value, "false", len) == 0)
        {
                if (result)
                        *result = false;
        }

        else if (pg_strncasecmp(value, "yes", len) == 0)
        {
                if (result)
                        *result = true;
        }
        else if (pg_strncasecmp(value, "no", len) == 0)
        {
                if (result)
                        *result = false;
        }

        /* 'o' is not unique enough */
        else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
        {
                if (result)
                        *result = true;
        }
        else if (pg_strncasecmp(value, "off", (len > 2 ? len : 2)) == 0)
        {
                if (result)
                        *result = false;
        }

        else if (pg_strcasecmp(value, "1") == 0)
        {
                if (result)
                        *result = true;
        }
        else if (pg_strcasecmp(value, "0") == 0)
        {
                if (result)
                        *result = false;
        }

        else
        {
                if (result)
                        *result = false;        /* suppress compiler warning */
                return false;
        }
        return true;
}



/*
 * Try to parse value as an integer.  The accepted formats are the
 * usual decimal, octal, or hexadecimal formats, optionally followed by
 * a unit name if "flags" indicates a unit is allowed.
 *
 * If the string parses okay, return true, else false.
 * If okay and result is not NULL, return the value in *result.
 * If not okay and hintmsg is not NULL, *hintmsg is set to a suitable
 *      HINT message, or NULL if no hint provided.
 */
bool
parse_int(const char *value, int *result, int flags, const char **hintmsg)
{
        int64           val;
        char       *endptr;

        /* To suppress compiler warnings, always set output params */
        if (result)
                *result = 0;
        if (hintmsg)
                *hintmsg = NULL;

        /* We assume here that int64 is at least as wide as long */
        errno = 0;
        val = strtol(value, &endptr, 0);

        if (endptr == value)
                return false;                   /* no HINT for integer syntax error */

        if (errno == ERANGE || val != (int64) ((int32) val))
        {
                if (hintmsg)
                        *hintmsg = gettext_noop("Value exceeds integer range.");
                return false;
        }

        /* allow whitespace between integer and unit */
        while (isspace((unsigned char) *endptr))
                endptr++;

        /* Handle possible unit */
        if (*endptr != '\0')
        {
                /*
                 * Note: the multiple-switch coding technique here is a bit tedious,
                 * but seems necessary to avoid intermediate-value overflows.
                 *
                 * If INT64_IS_BUSTED (ie, it's really int32) we will fail to detect
                 * overflow due to units conversion, but there are few enough such
                 * machines that it does not seem worth trying to be smarter.
                 */
                if (flags & GUC_UNIT_MEMORY)
                {
                        /* Set hint for use if no match or trailing garbage */
                        if (hintmsg)
                                *hintmsg = gettext_noop("Valid units for this parameter are \"kB\", \"MB\", and \"GB\".");

#if BLCKSZ < 1024 || BLCKSZ > (1024*1024)
#error BLCKSZ must be between 1KB and 1MB
#endif
#if XLOG_BLCKSZ < 1024 || XLOG_BLCKSZ > (1024*1024)
#error XLOG_BLCKSZ must be between 1KB and 1MB
#endif

                        if (strncmp(endptr, "kB", 2) == 0)
                        {
                                endptr += 2;
                                switch (flags & GUC_UNIT_MEMORY)
                                {
                                        case GUC_UNIT_BLOCKS:
                                                val /= (BLCKSZ / 1024);
                                                break;
                                        case GUC_UNIT_XBLOCKS:
                                                val /= (XLOG_BLCKSZ / 1024);
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "MB", 2) == 0)
                        {
                                endptr += 2;
                                switch (flags & GUC_UNIT_MEMORY)
                                {
                                        case GUC_UNIT_KB:
                                                val *= KB_PER_MB;
                                                break;
                                        case GUC_UNIT_BLOCKS:
                                                val *= KB_PER_MB / (BLCKSZ / 1024);
                                                break;
                                        case GUC_UNIT_XBLOCKS:
                                                val *= KB_PER_MB / (XLOG_BLCKSZ / 1024);
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "GB", 2) == 0)
                        {
                                endptr += 2;
                                switch (flags & GUC_UNIT_MEMORY)
                                {
                                        case GUC_UNIT_KB:
                                                val *= KB_PER_GB;
                                                break;
                                        case GUC_UNIT_BLOCKS:
                                                val *= KB_PER_GB / (BLCKSZ / 1024);
                                                break;
                                        case GUC_UNIT_XBLOCKS:
                                                val *= KB_PER_GB / (XLOG_BLCKSZ / 1024);
                                                break;
                                }
                        }
                }
                else if (flags & GUC_UNIT_TIME)
                {
                        /* Set hint for use if no match or trailing garbage */
                        if (hintmsg)
                                *hintmsg = gettext_noop("Valid units for this parameter are \"ms\", \"s\", \"min\", \"h\", and \"d\".");

                        if (strncmp(endptr, "ms", 2) == 0)
                        {
                                endptr += 2;
                                switch (flags & GUC_UNIT_TIME)
                                {
                                        case GUC_UNIT_S:
                                                val /= MS_PER_S;
                                                break;
                                        case GUC_UNIT_MIN:
                                                val /= MS_PER_MIN;
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "s", 1) == 0)
                        {
                                endptr += 1;
                                switch (flags & GUC_UNIT_TIME)
                                {
                                        case GUC_UNIT_MS:
                                                val *= MS_PER_S;
                                                break;
                                        case GUC_UNIT_MIN:
                                                val /= S_PER_MIN;
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "min", 3) == 0)
                        {
                                endptr += 3;
                                switch (flags & GUC_UNIT_TIME)
                                {
                                        case GUC_UNIT_MS:
                                                val *= MS_PER_MIN;
                                                break;
                                        case GUC_UNIT_S:
                                                val *= S_PER_MIN;
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "h", 1) == 0)
                        {
                                endptr += 1;
                                switch (flags & GUC_UNIT_TIME)
                                {
                                        case GUC_UNIT_MS:
                                                val *= MS_PER_H;
                                                break;
                                        case GUC_UNIT_S:
                                                val *= S_PER_H;
                                                break;
                                        case GUC_UNIT_MIN:
                                                val *= MIN_PER_H;
                                                break;
                                }
                        }
                        else if (strncmp(endptr, "d", 1) == 0)
                        {
                                endptr += 1;
                                switch (flags & GUC_UNIT_TIME)
                                {
                                        case GUC_UNIT_MS:
                                                val *= MS_PER_D;
                                                break;
                                        case GUC_UNIT_S:
                                                val *= S_PER_D;
                                                break;
                                        case GUC_UNIT_MIN:
                                                val *= MIN_PER_D;
                                                break;
                                }
                        }
                }

                /* allow whitespace after unit */
                while (isspace((unsigned char) *endptr))
                        endptr++;

                if (*endptr != '\0')
                        return false;           /* appropriate hint, if any, already set */

                /* Check for overflow due to units conversion */
                if (val != (int64) ((int32) val))
                {
                        if (hintmsg)
                                *hintmsg = gettext_noop("Value exceeds integer range.");
                        return false;
                }
        }

        if (result)
                *result = (int) val;
        return true;
}



/*
 * Try to parse value as a floating point number in the usual format.
 * If the string parses okay, return true, else false.
 * If okay and result is not NULL, return the value in *result.
 */
bool
parse_real(const char *value, double *result)
{
        double          val;
        char       *endptr;

        if (result)
                *result = 0;                    /* suppress compiler warning */

        errno = 0;
        val = strtod(value, &endptr);
        if (endptr == value || errno == ERANGE)
                return false;

        /* allow whitespace after number */
        while (isspace((unsigned char) *endptr))
                endptr++;
        if (*endptr != '\0')
                return false;

        if (result)
                *result = val;
        return true;
}


/*
 * Lookup the name for an enum option with the selected value.
 * Should only ever be called with known-valid values, so throws
 * an elog(ERROR) if the enum option is not found.
 *
 * The returned string is a pointer to static data and not
 * allocated for modification.
 */
const char *
config_enum_lookup_by_value(struct config_enum *record, int val)
{
        const struct config_enum_entry *entry;

        for (entry = record->options; entry && entry->name; entry++)
        {
                if (entry->val == val)
                        return entry->name;
        }

        elog(ERROR, "could not find enum option %d for %s",
                 val, record->gen.name);
        return NULL;            /* silence compiler */
}


/*
 * Lookup the value for an enum option with the selected name
 * (case-insensitive).
 * If the enum option is found, sets the retval value and returns
 * true. If it's not found, return FALSE and retval is set to 0.
 */
bool
config_enum_lookup_by_name(struct config_enum *record, const char *value,
                                                   int *retval)
{
        const struct config_enum_entry *entry;

        for (entry = record->options; entry && entry->name; entry++)
        {
                if (pg_strcasecmp(value, entry->name) == 0)
                {
                        *retval = entry->val;
                        return TRUE;
                }
        }

        *retval = 0;
        return FALSE;
}


/*
 * Return a list of all available options for an enum, excluding
 * hidden ones, separated by the given separator.
 * If prefix is non-NULL, it is added before the first enum value.
 * If suffix is non-NULL, it is added to the end of the string.
 */
static char *
config_enum_get_options(struct config_enum *record, const char *prefix,
                                                const char *suffix, const char *separator)
{
        const struct config_enum_entry *entry;
        StringInfoData  retstr;
        int                     seplen;

        initStringInfo(&retstr);
        appendStringInfoString(&retstr, prefix);
        
        seplen = strlen(separator);
        for (entry = record->options; entry && entry->name; entry++)
        {
                if (!entry->hidden)
                {
                        appendStringInfoString(&retstr, entry->name);
                        appendBinaryStringInfo(&retstr, separator, seplen);
                }
        }

        /*
         * All the entries may have been hidden, leaving the string empty
         * if no prefix was given. This indicates a broken GUC setup, since
         * there is no use for an enum without any values, so we just check
         * to make sure we don't write to invalid memory instead of actually
         * trying to do something smart with it.
         */
        if (retstr.len >= seplen)
        {
                /* Replace final separator */
                retstr.data[retstr.len - seplen] = '\0';
                retstr.len -= seplen;
        }

        appendStringInfoString(&retstr, suffix);

        return retstr.data;
}

/*
 * Call a GucStringAssignHook function, being careful to free the
 * "newval" string if the hook ereports.
 *
 * This is split out of set_config_option just to avoid the "volatile"
 * qualifiers that would otherwise have to be plastered all over.
 */
static const char *
call_string_assign_hook(GucStringAssignHook assign_hook,
                                                char *newval, bool doit, GucSource source)
{
        const char *result;

        PG_TRY();
        {
                result = (*assign_hook) (newval, doit, source);
        }
        PG_CATCH();
        {
                free(newval);
                PG_RE_THROW();
        }
        PG_END_TRY();

        return result;
}


/*
 * Sets option `name' to given value. The value should be a string
 * which is going to be parsed and converted to the appropriate data
 * type.  The context and source parameters indicate in which context this
 * function is being called so it can apply the access restrictions
 * properly.
 *
 * If value is NULL, set the option to its default value (normally the
 * reset_val, but if source == PGC_S_DEFAULT we instead use the boot_val).
 *
 * action indicates whether to set the value globally in the session, locally
 * to the current top transaction, or just for the duration of a function call.
 *
 * If changeVal is false then don't really set the option but do all
 * the checks to see if it would work.
 *
 * If there is an error (non-existing option, invalid value) then an
 * ereport(ERROR) is thrown *unless* this is called in a context where we
 * don't want to ereport (currently, startup or SIGHUP config file reread).
 * In that case we write a suitable error message via ereport(LOG) and
 * return false. This is working around the deficiencies in the ereport
 * mechanism, so don't blame me.  In all other cases, the function
 * returns true, including cases where the input is valid but we chose
 * not to apply it because of context or source-priority considerations.
 *
 * See also SetConfigOption for an external interface.
 */
bool
set_config_option(const char *name, const char *value,
                                  GucContext context, GucSource source,
                                  GucAction action, bool changeVal)
{
        struct config_generic *record;
        int                     elevel;
        bool            makeDefault;

        if (context == PGC_SIGHUP || source == PGC_S_DEFAULT)
        {
                /*
                 * To avoid cluttering the log, only the postmaster bleats loudly
                 * about problems with the config file.
                 */
                elevel = IsUnderPostmaster ? DEBUG3 : LOG;
        }
        else if (source == PGC_S_DATABASE || source == PGC_S_USER)
                elevel = WARNING;
        else
                elevel = ERROR;

        record = find_option(name, true, elevel);
        if (record == NULL)
        {
                ereport(elevel,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                           errmsg("unrecognized configuration parameter \"%s\"", name)));
                return false;
        }

        /*
         * If source is postgresql.conf, mark the found record with
         * GUC_IS_IN_FILE. This is for the convenience of ProcessConfigFile.  Note
         * that we do it even if changeVal is false, since ProcessConfigFile wants
         * the marking to occur during its testing pass.
         */
        if (source == PGC_S_FILE)
                record->status |= GUC_IS_IN_FILE;

        /*
         * Check if the option can be set at this time. See guc.h for the precise
         * rules. Note that we don't want to throw errors if we're in the SIGHUP
         * context. In that case we just ignore the attempt and return true.
         */
        switch (record->context)
        {
                case PGC_INTERNAL:
                        if (context == PGC_SIGHUP)
                                return true;
                        if (context != PGC_INTERNAL)
                        {
                                ereport(elevel,
                                                (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                                 errmsg("parameter \"%s\" cannot be changed",
                                                                name)));
                                return false;
                        }
                        break;
                case PGC_POSTMASTER:
                        if (context == PGC_SIGHUP)
                        {
                                /*
                                 * We are reading a PGC_POSTMASTER var from postgresql.conf.
                                 * We can't change the setting, so give a warning if the DBA
                                 * tries to change it.  (Throwing an error would be more
                                 * consistent, but seems overly rigid.)
                                 */
                                if (changeVal && !is_newvalue_equal(record, value))
                                        ereport(elevel,
                                                        (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                                         errmsg("attempted change of parameter \"%s\" ignored",
                                                                        name),
                                                         errdetail("This parameter cannot be changed after server start.")));
                                return true;
                        }
                        if (context != PGC_POSTMASTER)
                        {
                                ereport(elevel,
                                                (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                                 errmsg("attempted change of parameter \"%s\" ignored",
                                                                name),
                                                 errdetail("This parameter cannot be changed after server start.")));
                                return false;
                        }
                        break;
                case PGC_SIGHUP:
                        if (context != PGC_SIGHUP && context != PGC_POSTMASTER)
                        {
                                ereport(elevel,
                                                (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                                 errmsg("parameter \"%s\" cannot be changed now",
                                                                name)));
                                return false;
                        }

                        /*
                         * Hmm, the idea of the SIGHUP context is "ought to be global, but
                         * can be changed after postmaster start". But there's nothing
                         * that prevents a crafty administrator from sending SIGHUP
                         * signals to individual backends only.
                         */
                        break;
                case PGC_BACKEND:
                        if (context == PGC_SIGHUP)
                        {
                                /*
                                 * If a PGC_BACKEND parameter is changed in the config file,
                                 * we want to accept the new value in the postmaster (whence
                                 * it will propagate to subsequently-started backends), but
                                 * ignore it in existing backends.      This is a tad klugy, but
                                 * necessary because we don't re-read the config file during
                                 * backend start.
                                 */
                                if (IsUnderPostmaster)
                                        return true;
                        }
                        else if (context != PGC_BACKEND && context != PGC_POSTMASTER)
                        {
                                ereport(elevel,
                                                (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                                 errmsg("parameter \"%s\" cannot be set after connection start",
                                                                name)));
                                return false;
                        }
                        break;
                case PGC_SUSET:
                        if (context == PGC_USERSET || context == PGC_BACKEND)
                        {
                                ereport(elevel,
                                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                                 errmsg("permission denied to set parameter \"%s\"",
                                                                name)));
                                return false;
                        }
                        break;
                case PGC_USERSET:
                        /* always okay */
                        break;
        }

        /*
         * Should we set reset/stacked values?  (If so, the behavior is not
         * transactional.)      This is done either when we get a default value from
         * the database's/user's/client's default settings or when we reset a
         * value to its default.
         */
        makeDefault = changeVal && (source <= PGC_S_OVERRIDE) &&
                ((value != NULL) || source == PGC_S_DEFAULT);

        /*
         * Ignore attempted set if overridden by previously processed setting.
         * However, if changeVal is false then plow ahead anyway since we are
         * trying to find out if the value is potentially good, not actually use
         * it. Also keep going if makeDefault is true, since we may want to set
         * the reset/stacked values even if we can't set the variable itself.
         */
        if (record->source > source)
        {
                if (changeVal && !makeDefault)
                {
                        elog(DEBUG3, "\"%s\": setting ignored because previous source is higher priority",
                                 name);
                        return true;
                }
                changeVal = false;
        }

        /*
         * Evaluate value and set variable.
         */
        switch (record->vartype)
        {
                case PGC_BOOL:
                        {
                                struct config_bool *conf = (struct config_bool *) record;
                                bool            newval;

                                if (value)
                                {
                                        if (!parse_bool(value, &newval))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                  errmsg("parameter \"%s\" requires a Boolean value",
                                                                 name)));
                                                return false;
                                        }
                                }
                                else if (source == PGC_S_DEFAULT)
                                        newval = conf->boot_val;
                                else
                                {
                                        newval = conf->reset_val;
                                        source = conf->gen.reset_source;
                                }

                                /* Save old value to support transaction abort */
                                if (changeVal && !makeDefault)
                                        push_old_value(&conf->gen, action);

                                if (conf->assign_hook)
                                        if (!(*conf->assign_hook) (newval, changeVal, source))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                         errmsg("invalid value for parameter \"%s\": %d",
                                                                        name, (int) newval)));
                                                return false;
                                        }

                                if (changeVal)
                                {
                                        *conf->variable = newval;
                                        conf->gen.source = source;
                                }
                                if (makeDefault)
                                {
                                        GucStack   *stack;

                                        if (conf->gen.reset_source <= source)
                                        {
                                                conf->reset_val = newval;
                                                conf->gen.reset_source = source;
                                        }
                                        for (stack = conf->gen.stack; stack; stack = stack->prev)
                                        {
                                                if (stack->source <= source)
                                                {
                                                        stack->prior.boolval = newval;
                                                        stack->source = source;
                                                }
                                        }
                                }
                                break;
                        }

                case PGC_INT:
                        {
                                struct config_int *conf = (struct config_int *) record;
                                int                     newval;

                                if (value)
                                {
                                        const char *hintmsg;

                                        if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                 errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                                name, value),
                                                                 hintmsg ? errhint("%s", hintmsg) : 0));
                                                return false;
                                        }
                                        if (newval < conf->min || newval > conf->max)
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                                 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
                                                                                newval, name, conf->min, conf->max)));
                                                return false;
                                        }
                                }
                                else if (source == PGC_S_DEFAULT)
                                        newval = conf->boot_val;
                                else
                                {
                                        newval = conf->reset_val;
                                        source = conf->gen.reset_source;
                                }

                                /* Save old value to support transaction abort */
                                if (changeVal && !makeDefault)
                                        push_old_value(&conf->gen, action);

                                if (conf->assign_hook)
                                        if (!(*conf->assign_hook) (newval, changeVal, source))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                         errmsg("invalid value for parameter \"%s\": %d",
                                                                        name, newval)));
                                                return false;
                                        }

                                if (changeVal)
                                {
                                        *conf->variable = newval;
                                        conf->gen.source = source;
                                }
                                if (makeDefault)
                                {
                                        GucStack   *stack;

                                        if (conf->gen.reset_source <= source)
                                        {
                                                conf->reset_val = newval;
                                                conf->gen.reset_source = source;
                                        }
                                        for (stack = conf->gen.stack; stack; stack = stack->prev)
                                        {
                                                if (stack->source <= source)
                                                {
                                                        stack->prior.intval = newval;
                                                        stack->source = source;
                                                }
                                        }
                                }
                                break;
                        }

                case PGC_REAL:
                        {
                                struct config_real *conf = (struct config_real *) record;
                                double          newval;

                                if (value)
                                {
                                        if (!parse_real(value, &newval))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                  errmsg("parameter \"%s\" requires a numeric value",
                                                                 name)));
                                                return false;
                                        }
                                        if (newval < conf->min || newval > conf->max)
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                                 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
                                                                                newval, name, conf->min, conf->max)));
                                                return false;
                                        }
                                }
                                else if (source == PGC_S_DEFAULT)
                                        newval = conf->boot_val;
                                else
                                {
                                        newval = conf->reset_val;
                                        source = conf->gen.reset_source;
                                }

                                /* Save old value to support transaction abort */
                                if (changeVal && !makeDefault)
                                        push_old_value(&conf->gen, action);

                                if (conf->assign_hook)
                                        if (!(*conf->assign_hook) (newval, changeVal, source))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                         errmsg("invalid value for parameter \"%s\": %g",
                                                                        name, newval)));
                                                return false;
                                        }

                                if (changeVal)
                                {
                                        *conf->variable = newval;
                                        conf->gen.source = source;
                                }
                                if (makeDefault)
                                {
                                        GucStack   *stack;

                                        if (conf->gen.reset_source <= source)
                                        {
                                                conf->reset_val = newval;
                                                conf->gen.reset_source = source;
                                        }
                                        for (stack = conf->gen.stack; stack; stack = stack->prev)
                                        {
                                                if (stack->source <= source)
                                                {
                                                        stack->prior.realval = newval;
                                                        stack->source = source;
                                                }
                                        }
                                }
                                break;
                        }

                case PGC_STRING:
                        {
                                struct config_string *conf = (struct config_string *) record;
                                char       *newval;

                                if (value)
                                {
                                        newval = guc_strdup(elevel, value);
                                        if (newval == NULL)
                                                return false;

                                        /*
                                         * The only sort of "parsing" check we need to do is apply
                                         * truncation if GUC_IS_NAME.
                                         */
                                        if (conf->gen.flags & GUC_IS_NAME)
                                                truncate_identifier(newval, strlen(newval), true);
                                }
                                else if (source == PGC_S_DEFAULT)
                                {
                                        if (conf->boot_val == NULL)
                                                newval = NULL;
                                        else
                                        {
                                                newval = guc_strdup(elevel, conf->boot_val);
                                                if (newval == NULL)
                                                        return false;
                                        }
                                }
                                else
                                {
                                        /*
                                         * We could possibly avoid strdup here, but easier to make
                                         * this case work the same as the normal assignment case;
                                         * note the possible free of newval below.
                                         */
                                        if (conf->reset_val == NULL)
                                                newval = NULL;
                                        else
                                        {
                                                newval = guc_strdup(elevel, conf->reset_val);
                                                if (newval == NULL)
                                                        return false;
                                        }
                                        source = conf->gen.reset_source;
                                }

                                /* Save old value to support transaction abort */
                                if (changeVal && !makeDefault)
                                        push_old_value(&conf->gen, action);

                                if (conf->assign_hook && newval)
                                {
                                        const char *hookresult;

                                        /*
                                         * If the hook ereports, we have to make sure we free
                                         * newval, else it will be a permanent memory leak.
                                         */
                                        hookresult = call_string_assign_hook(conf->assign_hook,
                                                                                                                 newval,
                                                                                                                 changeVal,
                                                                                                                 source);
                                        if (hookresult == NULL)
                                        {
                                                free(newval);
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                 errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                                name, value ? value : "")));
                                                return false;
                                        }
                                        else if (hookresult != newval)
                                        {
                                                free(newval);

                                                /*
                                                 * Having to cast away const here is annoying, but the
                                                 * alternative is to declare assign_hooks as returning
                                                 * char*, which would mean they'd have to cast away
                                                 * const, or as both taking and returning char*, which
                                                 * doesn't seem attractive either --- we don't want
                                                 * them to scribble on the passed str.
                                                 */
                                                newval = (char *) hookresult;
                                        }
                                }

                                if (changeVal)
                                {
                                        set_string_field(conf, conf->variable, newval);
                                        conf->gen.source = source;
                                }
                                if (makeDefault)
                                {
                                        GucStack   *stack;

                                        if (conf->gen.reset_source <= source)
                                        {
                                                set_string_field(conf, &conf->reset_val, newval);
                                                conf->gen.reset_source = source;
                                        }
                                        for (stack = conf->gen.stack; stack; stack = stack->prev)
                                        {
                                                if (stack->source <= source)
                                                {
                                                        set_string_field(conf, &stack->prior.stringval,
                                                                                         newval);
                                                        stack->source = source;
                                                }
                                        }
                                }
                                /* Perhaps we didn't install newval anywhere */
                                if (newval && !string_field_used(conf, newval))
                                        free(newval);
                                break;
                        }
                case PGC_ENUM:
                        {
                                struct config_enum *conf = (struct config_enum *) record;
                                int                     newval;

                                if (value)
                                {
                                        if (!config_enum_lookup_by_name(conf, value, &newval))
                                        {
                                                char *hintmsg;
                                           
                                                hintmsg = config_enum_get_options(conf,
                                                                                                                  "Available values: ",
                                                                                                                  ".", ", ");

                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                                 errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                                                name, value),
                                                                 hintmsg ? errhint("%s", hintmsg) : 0));

                                                if (hintmsg)
                                                        pfree(hintmsg);
                                                return false;
                                        }
                                }
                                else if (source == PGC_S_DEFAULT)
                                        newval = conf->boot_val;
                                else
                                {
                                        newval = conf->reset_val;
                                        source = conf->gen.reset_source;
                                }

                                /* Save old value to support transaction abort */
                                if (changeVal && !makeDefault)
                                        push_old_value(&conf->gen, action);

                                if (conf->assign_hook)
                                        if (!(*conf->assign_hook) (newval, changeVal, source))
                                        {
                                                ereport(elevel,
                                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                                 errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                                                name, 
                                                                                config_enum_lookup_by_value(conf, newval))));
                                                return false;
                                        }

                                if (changeVal)
                                {
                                        *conf->variable = newval;
                                        conf->gen.source = source;
                                }
                                if (makeDefault)
                                {
                                        GucStack   *stack;

                                        if (conf->gen.reset_source <= source)
                                        {
                                                conf->reset_val = newval;
                                                conf->gen.reset_source = source;
                                        }
                                        for (stack = conf->gen.stack; stack; stack = stack->prev)
                                        {
                                                if (stack->source <= source)
                                                {
                                                        stack->prior.enumval = newval;
                                                        stack->source = source;
                                                }
                                        }
                                }
                                break;
                        }
        }

        if (changeVal && (record->flags & GUC_REPORT))
                ReportGUCOption(record);

        return true;
}


/*
 * Set the fields for source file and line number the setting came from.
 */
static void
set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
{
        struct config_generic *record;
        int                     elevel;

        /*
         * To avoid cluttering the log, only the postmaster bleats loudly
         * about problems with the config file.
         */
        elevel = IsUnderPostmaster ? DEBUG3 : LOG;

        record = find_option(name, true, elevel);
        /* should not happen */
        if (record == NULL)
                elog(ERROR, "unrecognized configuration parameter \"%s\"", name);

        sourcefile = guc_strdup(elevel, sourcefile);
        if (record->sourcefile)
                free(record->sourcefile);
        record->sourcefile = sourcefile;
        record->sourceline = sourceline;
}

/*
 * Set a config option to the given value. See also set_config_option,
 * this is just the wrapper to be called from outside GUC.      NB: this
 * is used only for non-transactional operations.
 *
 * Note: there is no support here for setting source file/line, as it
 * is currently not needed.
 */
void
SetConfigOption(const char *name, const char *value,
                                GucContext context, GucSource source)
{
        (void) set_config_option(name, value, context, source,
                                                         GUC_ACTION_SET, true);
}



/*
 * Fetch the current value of the option `name'. If the option doesn't exist,
 * throw an ereport and don't return.
 *
 * The string is *not* allocated for modification and is really only
 * valid until the next call to configuration related functions.
 */
const char *
GetConfigOption(const char *name)
{
        struct config_generic *record;
        static char buffer[256];

        record = find_option(name, false, ERROR);
        if (record == NULL)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                           errmsg("unrecognized configuration parameter \"%s\"", name)));
        if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
                ereport(ERROR,
                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                 errmsg("must be superuser to examine \"%s\"", name)));

        switch (record->vartype)
        {
                case PGC_BOOL:
                        return *((struct config_bool *) record)->variable ? "on" : "off";

                case PGC_INT:
                        snprintf(buffer, sizeof(buffer), "%d",
                                         *((struct config_int *) record)->variable);
                        return buffer;

                case PGC_REAL:
                        snprintf(buffer, sizeof(buffer), "%g",
                                         *((struct config_real *) record)->variable);
                        return buffer;

                case PGC_STRING:
                        return *((struct config_string *) record)->variable;

                case PGC_ENUM:
                        return config_enum_lookup_by_value((struct config_enum *) record,
                                                                                        *((struct config_enum *) record)->variable);
        }
        return NULL;
}

/*
 * Get the RESET value associated with the given option.
 *
 * Note: this is not re-entrant, due to use of static result buffer;
 * not to mention that a string variable could have its reset_val changed.
 * Beware of assuming the result value is good for very long.
 */
const char *
GetConfigOptionResetString(const char *name)
{
        struct config_generic *record;
        static char buffer[256];

        record = find_option(name, false, ERROR);
        if (record == NULL)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                           errmsg("unrecognized configuration parameter \"%s\"", name)));
        if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
                ereport(ERROR,
                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                 errmsg("must be superuser to examine \"%s\"", name)));

        switch (record->vartype)
        {
                case PGC_BOOL:
                        return ((struct config_bool *) record)->reset_val ? "on" : "off";

                case PGC_INT:
                        snprintf(buffer, sizeof(buffer), "%d",
                                         ((struct config_int *) record)->reset_val);
                        return buffer;

                case PGC_REAL:
                        snprintf(buffer, sizeof(buffer), "%g",
                                         ((struct config_real *) record)->reset_val);
                        return buffer;

                case PGC_STRING:
                        return ((struct config_string *) record)->reset_val;

                case PGC_ENUM:
                        return config_enum_lookup_by_value((struct config_enum *) record,
                                                                                    ((struct config_enum *) record)->reset_val);
        }
        return NULL;
}

/*
 * Detect whether the given configuration option can only be set by
 * a superuser.
 */
bool
IsSuperuserConfigOption(const char *name)
{
        struct config_generic *record;

        record = find_option(name, false, ERROR);
        /* On an unrecognized name, don't error, just return false. */
        if (record == NULL)
                return false;
        return (record->context == PGC_SUSET);
}


/*
 * GUC_complaint_elevel
 *              Get the ereport error level to use in an assign_hook's error report.
 *
 * This should be used by assign hooks that want to emit a custom error
 * report (in addition to the generic "invalid value for option FOO" that
 * guc.c will provide).  Note that the result might be ERROR or a lower
 * level, so the caller must be prepared for control to return from ereport,
 * or not.  If control does return, return false/NULL from the hook function.
 *
 * At some point it'd be nice to replace this with a mechanism that allows
 * the custom message to become the DETAIL line of guc.c's generic message.
 */
int
GUC_complaint_elevel(GucSource source)
{
        int                     elevel;

        if (source == PGC_S_FILE)
        {
                /*
                 * To avoid cluttering the log, only the postmaster bleats loudly
                 * about problems with the config file.
                 */
                elevel = IsUnderPostmaster ? DEBUG3 : LOG;
        }
        else if (source == PGC_S_OVERRIDE)
        {
                /*
                 * If we're a postmaster child, this is probably "undo" during
                 * transaction abort, so we don't want to clutter the log.  There's
                 * a small chance of a real problem with an OVERRIDE setting,
                 * though, so suppressing the message entirely wouldn't be desirable.
                 */
                elevel = IsUnderPostmaster ? DEBUG5 : LOG;
        }
        else if (source < PGC_S_INTERACTIVE)
                elevel = LOG;
        else
                elevel = ERROR;

        return elevel;
}


/*
 * flatten_set_variable_args
 *              Given a parsenode List as emitted by the grammar for SET,
 *              convert to the flat string representation used by GUC.
 *
 * We need to be told the name of the variable the args are for, because
 * the flattening rules vary (ugh).
 *
 * The result is NULL if args is NIL (ie, SET ... TO DEFAULT), otherwise
 * a palloc'd string.
 */
static char *
flatten_set_variable_args(const char *name, List *args)
{
        struct config_generic *record;
        int                     flags;
        StringInfoData buf;
        ListCell   *l;

        /* Fast path if just DEFAULT */
        if (args == NIL)
                return NULL;

        /* Else get flags for the variable */
        record = find_option(name, true, ERROR);
        if (record == NULL)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                           errmsg("unrecognized configuration parameter \"%s\"", name)));

        flags = record->flags;

        /* Complain if list input and non-list variable */
        if ((flags & GUC_LIST_INPUT) == 0 &&
                list_length(args) != 1)
                ereport(ERROR,
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("SET %s takes only one argument", name)));

        initStringInfo(&buf);

        /*
         * Each list member may be a plain A_Const node, or an A_Const within a
         * TypeCast; the latter case is supported only for ConstInterval
         * arguments (for SET TIME ZONE).
         */
        foreach(l, args)
        {
                Node       *arg = (Node *) lfirst(l);
                char       *val;
                TypeName   *typename = NULL;
                A_Const    *con;

                if (l != list_head(args))
                        appendStringInfo(&buf, ", ");

                if (IsA(arg, TypeCast))
                {
                        TypeCast *tc = (TypeCast *) arg;

                        arg = tc->arg;
                        typename = tc->typename;
                }

                if (!IsA(arg, A_Const))
                        elog(ERROR, "unrecognized node type: %d", (int) nodeTag(arg));
                con = (A_Const *) arg;

                switch (nodeTag(&con->val))
                {
                        case T_Integer:
                                appendStringInfo(&buf, "%ld", intVal(&con->val));
                                break;
                        case T_Float:
                                /* represented as a string, so just copy it */
                                appendStringInfoString(&buf, strVal(&con->val));
                                break;
                        case T_String:
                                val = strVal(&con->val);
                                if (typename != NULL)
                                {
                                        /*
                                         * Must be a ConstInterval argument for TIME ZONE. Coerce
                                         * to interval and back to normalize the value and account
                                         * for any typmod.
                                         */
                                        Oid                     typoid;
                                        int32           typmod;
                                        Datum           interval;
                                        char       *intervalout;

                                        typoid = typenameTypeId(NULL, typename, &typmod);
                                        Assert(typoid == INTERVALOID);

                                        interval =
                                                DirectFunctionCall3(interval_in,
                                                                                        CStringGetDatum(val),
                                                                                        ObjectIdGetDatum(InvalidOid),
                                                                                        Int32GetDatum(typmod));

                                        intervalout =
                                                DatumGetCString(DirectFunctionCall1(interval_out,
                                                                                                                        interval));
                                        appendStringInfo(&buf, "INTERVAL '%s'", intervalout);
                                }
                                else
                                {
                                        /*
                                         * Plain string literal or identifier.  For quote mode,
                                         * quote it if it's not a vanilla identifier.
                                         */
                                        if (flags & GUC_LIST_QUOTE)
                                                appendStringInfoString(&buf, quote_identifier(val));
                                        else
                                                appendStringInfoString(&buf, val);
                                }
                                break;
                        default:
                                elog(ERROR, "unrecognized node type: %d",
                                         (int) nodeTag(&con->val));
                                break;
                }
        }

        return buf.data;
}


/*
 * SET command
 */
void
ExecSetVariableStmt(VariableSetStmt *stmt)
{
        GucAction       action = stmt->is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET;

        switch (stmt->kind)
        {
                case VAR_SET_VALUE:
                case VAR_SET_CURRENT:
                        set_config_option(stmt->name,
                                                          ExtractSetVariableArgs(stmt),
                                                          (superuser() ? PGC_SUSET : PGC_USERSET),
                                                          PGC_S_SESSION,
                                                          action,
                                                          true);
                        break;
                case VAR_SET_MULTI:

                        /*
                         * Special case for special SQL syntax that effectively sets more
                         * than one variable per statement.
                         */
                        if (strcmp(stmt->name, "TRANSACTION") == 0)
                        {
                                ListCell   *head;

                                foreach(head, stmt->args)
                                {
                                        DefElem    *item = (DefElem *) lfirst(head);

                                        if (strcmp(item->defname, "transaction_isolation") == 0)
                                                SetPGVariable("transaction_isolation",
                                                                          list_make1(item->arg), stmt->is_local);
                                        else if (strcmp(item->defname, "transaction_read_only") == 0)
                                                SetPGVariable("transaction_read_only",
                                                                          list_make1(item->arg), stmt->is_local);
                                        else
                                                elog(ERROR, "unexpected SET TRANSACTION element: %s",
                                                         item->defname);
                                }
                        }
                        else if (strcmp(stmt->name, "SESSION CHARACTERISTICS") == 0)
                        {
                                ListCell   *head;

                                foreach(head, stmt->args)
                                {
                                        DefElem    *item = (DefElem *) lfirst(head);

                                        if (strcmp(item->defname, "transaction_isolation") == 0)
                                                SetPGVariable("default_transaction_isolation",
                                                                          list_make1(item->arg), stmt->is_local);
                                        else if (strcmp(item->defname, "transaction_read_only") == 0)
                                                SetPGVariable("default_transaction_read_only",
                                                                          list_make1(item->arg), stmt->is_local);
                                        else
                                                elog(ERROR, "unexpected SET SESSION element: %s",
                                                         item->defname);
                                }
                        }
                        else
                                elog(ERROR, "unexpected SET MULTI element: %s",
                                         stmt->name);
                        break;
                case VAR_SET_DEFAULT:
                case VAR_RESET:
                        set_config_option(stmt->name,
                                                          NULL,
                                                          (superuser() ? PGC_SUSET : PGC_USERSET),
                                                          PGC_S_SESSION,
                                                          action,
                                                          true);
                        break;
                case VAR_RESET_ALL:
                        ResetAllOptions();
                        break;
        }
}

/*
 * Get the value to assign for a VariableSetStmt, or NULL if it's RESET.
 * The result is palloc'd.
 *
 * This is exported for use by actions such as ALTER ROLE SET.
 */
char *
ExtractSetVariableArgs(VariableSetStmt *stmt)
{
        switch (stmt->kind)
        {
                case VAR_SET_VALUE:
                        return flatten_set_variable_args(stmt->name, stmt->args);
                case VAR_SET_CURRENT:
                        return GetConfigOptionByName(stmt->name, NULL);
                default:
                        return NULL;
        }
}

/*
 * SetPGVariable - SET command exported as an easily-C-callable function.
 *
 * This provides access to SET TO value, as well as SET TO DEFAULT (expressed
 * by passing args == NIL), but not SET FROM CURRENT functionality.
 */
void
SetPGVariable(const char *name, List *args, bool is_local)
{
        char       *argstring = flatten_set_variable_args(name, args);

        /* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
        set_config_option(name,
                                          argstring,
                                          (superuser() ? PGC_SUSET : PGC_USERSET),
                                          PGC_S_SESSION,
                                          is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
                                          true);
}

/*
 * SET command wrapped as a SQL callable function.
 */
Datum
set_config_by_name(PG_FUNCTION_ARGS)
{
        char       *name;
        char       *value;
        char       *new_value;
        bool            is_local;

        if (PG_ARGISNULL(0))
                ereport(ERROR,
                                (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                                 errmsg("SET requires parameter name")));

        /* Get the GUC variable name */
        name = TextDatumGetCString(PG_GETARG_DATUM(0));

        /* Get the desired value or set to NULL for a reset request */
        if (PG_ARGISNULL(1))
                value = NULL;
        else
                value = TextDatumGetCString(PG_GETARG_DATUM(1));

        /*
         * Get the desired state of is_local. Default to false if provided value
         * is NULL
         */
        if (PG_ARGISNULL(2))
                is_local = false;
        else
                is_local = PG_GETARG_BOOL(2);

        /* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
        set_config_option(name,
                                          value,
                                          (superuser() ? PGC_SUSET : PGC_USERSET),
                                          PGC_S_SESSION,
                                          is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
                                          true);

        /* get the new current value */
        new_value = GetConfigOptionByName(name, NULL);

        /* Convert return string to text */
        PG_RETURN_TEXT_P(cstring_to_text(new_value));
}


/*
 * Common code for DefineCustomXXXVariable subroutines: allocate the
 * new variable's config struct and fill in generic fields.
 */
static struct config_generic *
init_custom_variable(const char *name,
                                         const char *short_desc,
                                         const char *long_desc,
                                         GucContext context,
                                         int flags,
                                         enum config_type type,
                                         size_t sz)
{
        struct config_generic *gen;

        /*
         * Only allow custom PGC_POSTMASTER variables to be created during
         * shared library preload; any later than that, we can't ensure that
         * the value doesn't change after startup.  This is a fatal elog if it
         * happens; just erroring out isn't safe because we don't know what
         * the calling loadable module might already have hooked into.
         */
        if (context == PGC_POSTMASTER &&
                !process_shared_preload_libraries_in_progress)
                elog(FATAL, "cannot create PGC_POSTMASTER variables after startup");

        gen = (struct config_generic *) guc_malloc(ERROR, sz);
        memset(gen, 0, sz);

        gen->name = guc_strdup(ERROR, name);
        gen->context = context;
        gen->group = CUSTOM_OPTIONS;
        gen->short_desc = short_desc;
        gen->long_desc = long_desc;
        gen->flags = flags;
        gen->vartype = type;

        return gen;
}

/*
 * Common code for DefineCustomXXXVariable subroutines: insert the new
 * variable into the GUC variable array, replacing any placeholder.
 */
static void
define_custom_variable(struct config_generic * variable)
{
        const char *name = variable->name;
        const char **nameAddr = &name;
        const char *value;
        struct config_string *pHolder;
        GucContext phcontext;
        struct config_generic **res;

        /*
         * See if there's a placeholder by the same name.
         */
        res = (struct config_generic **) bsearch((void *) &nameAddr,
                                                                                         (void *) guc_variables,
                                                                                         num_guc_variables,
                                                                                         sizeof(struct config_generic *),
                                                                                         guc_var_compare);
        if (res == NULL)
        {
                /*
                 * No placeholder to replace, so we can just add it ... but first,
                 * make sure it's initialized to its default value.
                 */
                InitializeOneGUCOption(variable);
                add_guc_variable(variable, ERROR);
                return;
        }

        /*
         * This better be a placeholder
         */
        if (((*res)->flags & GUC_CUSTOM_PLACEHOLDER) == 0)
                ereport(ERROR,
                                (errcode(ERRCODE_INTERNAL_ERROR),
                                 errmsg("attempt to redefine parameter \"%s\"", name)));

        Assert((*res)->vartype == PGC_STRING);
        pHolder = (struct config_string *) (*res);

        /*
         * First, set the variable to its default value.  We must do this even
         * though we intend to immediately apply a new value, since it's possible
         * that the new value is invalid.
         */
        InitializeOneGUCOption(variable);

        /*
         * Replace the placeholder. We aren't changing the name, so no re-sorting
         * is necessary
         */
        *res = variable;

        /*
         * Infer context for assignment based on source of existing value.
         * We can't tell this with exact accuracy, but we can at least do
         * something reasonable in typical cases.
         */
        switch (pHolder->gen.source)
        {
                case PGC_S_DEFAULT:
                case PGC_S_ENV_VAR:
                case PGC_S_FILE:
                case PGC_S_ARGV:
                        /*
                         * If we got past the check in init_custom_variable, we can
                         * safely assume that any existing value for a PGC_POSTMASTER
                         * variable was set in postmaster context.
                         */
                        if (variable->context == PGC_POSTMASTER)
                                phcontext = PGC_POSTMASTER;
                        else
                                phcontext = PGC_SIGHUP;
                        break;
                case PGC_S_DATABASE:
                case PGC_S_USER:
                case PGC_S_CLIENT:
                case PGC_S_SESSION:
                default:
                        phcontext = PGC_USERSET;
                        break;
        }

        /*
         * Assign the string value stored in the placeholder to the real variable.
         *
         * XXX this is not really good enough --- it should be a nontransactional
         * assignment, since we don't want it to roll back if the current xact
         * fails later.  (Or do we?)
         */
        value = *pHolder->variable;

        if (value)
        {
                if (set_config_option(name, value,
                                                          phcontext, pHolder->gen.source,
                                                          GUC_ACTION_SET, true))
                {
                        /* Also copy over any saved source-location information */
                        if (pHolder->gen.sourcefile)
                                set_config_sourcefile(name, pHolder->gen.sourcefile,
                                                                          pHolder->gen.sourceline);
                }
        }

        /*
         * Free up as much as we conveniently can of the placeholder structure
         * (this neglects any stack items...)
         */
        set_string_field(pHolder, pHolder->variable, NULL);
        set_string_field(pHolder, &pHolder->reset_val, NULL);

        free(pHolder);
}

void
DefineCustomBoolVariable(const char *name,
                                                 const char *short_desc,
                                                 const char *long_desc,
                                                 bool *valueAddr,
                                                 bool bootValue,
                                                 GucContext context,
                                                 int flags,
                                                 GucBoolAssignHook assign_hook,
                                                 GucShowHook show_hook)
{
        struct config_bool *var;

        var = (struct config_bool *)
                init_custom_variable(name, short_desc, long_desc, context, flags,
                                                         PGC_BOOL, sizeof(struct config_bool));
        var->variable = valueAddr;
        var->boot_val = bootValue;
        var->reset_val = bootValue;
        var->assign_hook = assign_hook;
        var->show_hook = show_hook;
        define_custom_variable(&var->gen);
}

void
DefineCustomIntVariable(const char *name,
                                                const char *short_desc,
                                                const char *long_desc,
                                                int *valueAddr,
                                                int bootValue,
                                                int minValue,
                                                int maxValue,
                                                GucContext context,
                                                int flags,
                                                GucIntAssignHook assign_hook,
                                                GucShowHook show_hook)
{
        struct config_int *var;

        var = (struct config_int *)
                init_custom_variable(name, short_desc, long_desc, context, flags,
                                                         PGC_INT, sizeof(struct config_int));
        var->variable = valueAddr;
        var->boot_val = bootValue;
        var->reset_val = bootValue;
        var->min = minValue;
        var->max = maxValue;
        var->assign_hook = assign_hook;
        var->show_hook = show_hook;
        define_custom_variable(&var->gen);
}

void
DefineCustomRealVariable(const char *name,
                                                 const char *short_desc,
                                                 const char *long_desc,
                                                 double *valueAddr,
                                                 double bootValue,
                                                 double minValue,
                                                 double maxValue,
                                                 GucContext context,
                                                 int flags,
                                                 GucRealAssignHook assign_hook,
                                                 GucShowHook show_hook)
{
        struct config_real *var;

        var = (struct config_real *)
                init_custom_variable(name, short_desc, long_desc, context, flags,
                                                         PGC_REAL, sizeof(struct config_real));
        var->variable = valueAddr;
        var->boot_val = bootValue;
        var->reset_val = bootValue;
        var->min = minValue;
        var->max = maxValue;
        var->assign_hook = assign_hook;
        var->show_hook = show_hook;
        define_custom_variable(&var->gen);
}

void
DefineCustomStringVariable(const char *name,
                                                   const char *short_desc,
                                                   const char *long_desc,
                                                   char **valueAddr,
                                                   const char *bootValue,
                                                   GucContext context,
                                                   int flags,
                                                   GucStringAssignHook assign_hook,
                                                   GucShowHook show_hook)
{
        struct config_string *var;

        var = (struct config_string *)
                init_custom_variable(name, short_desc, long_desc, context, flags,
                                                         PGC_STRING, sizeof(struct config_string));
        var->variable = valueAddr;
        var->boot_val = bootValue;
        /* we could probably do without strdup, but keep it like normal case */
        if (var->boot_val)
                var->reset_val = guc_strdup(ERROR, var->boot_val);
        var->assign_hook = assign_hook;
        var->show_hook = show_hook;
        define_custom_variable(&var->gen);
}

void
DefineCustomEnumVariable(const char *name,
                                                 const char *short_desc,
                                                 const char *long_desc,
                                                 int *valueAddr,
                                                 int bootValue,
                                                 const struct config_enum_entry *options,
                                                 GucContext context,
                                                 int flags,
                                                 GucEnumAssignHook assign_hook,
                                                 GucShowHook show_hook)
{
        struct config_enum *var;

        var = (struct config_enum *)
                init_custom_variable(name, short_desc, long_desc, context, flags,
                                                         PGC_ENUM, sizeof(struct config_enum));
        var->variable = valueAddr;
        var->boot_val = bootValue;
        var->reset_val = bootValue;
        var->options = options;
        var->assign_hook = assign_hook;
        var->show_hook = show_hook;
        define_custom_variable(&var->gen);
}

void
EmitWarningsOnPlaceholders(const char *className)
{
        int                     classLen = strlen(className);
        int                     i;

        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *var = guc_variables[i];

                if ((var->flags & GUC_CUSTOM_PLACEHOLDER) != 0 &&
                        strncmp(className, var->name, classLen) == 0 &&
                        var->name[classLen] == GUC_QUALIFIER_SEPARATOR)
                {
                        ereport(WARNING,
                                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                                         errmsg("unrecognized configuration parameter \"%s\"",
                                                        var->name)));
                }
        }
}


/*
 * SHOW command
 */
void
GetPGVariable(const char *name, DestReceiver *dest)
{
        if (guc_name_compare(name, "all") == 0)
                ShowAllGUCConfig(dest);
        else
                ShowGUCConfigOption(name, dest);
}

TupleDesc
GetPGVariableResultDesc(const char *name)
{
        TupleDesc       tupdesc;

        if (guc_name_compare(name, "all") == 0)
        {
                /* need a tuple descriptor representing three TEXT columns */
                tupdesc = CreateTemplateTupleDesc(3, false);
                TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
                                                   TEXTOID, -1, 0);
        }
        else
        {
                const char *varname;

                /* Get the canonical spelling of name */
                (void) GetConfigOptionByName(name, &varname);

                /* need a tuple descriptor representing a single TEXT column */
                tupdesc = CreateTemplateTupleDesc(1, false);
                TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
                                                   TEXTOID, -1, 0);
        }
        return tupdesc;
}


/*
 * SHOW command
 */
static void
ShowGUCConfigOption(const char *name, DestReceiver *dest)
{
        TupOutputState *tstate;
        TupleDesc       tupdesc;
        const char *varname;
        char       *value;

        /* Get the value and canonical spelling of name */
        value = GetConfigOptionByName(name, &varname);

        /* need a tuple descriptor representing a single TEXT column */
        tupdesc = CreateTemplateTupleDesc(1, false);
        TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
                                           TEXTOID, -1, 0);

        /* prepare for projection of tuples */
        tstate = begin_tup_output_tupdesc(dest, tupdesc);

        /* Send it */
        do_text_output_oneline(tstate, value);

        end_tup_output(tstate);
}

/*
 * SHOW ALL command
 */
static void
ShowAllGUCConfig(DestReceiver *dest)
{
        bool            am_superuser = superuser();
        int                     i;
        TupOutputState *tstate;
        TupleDesc       tupdesc;
        char       *values[3];

        /* need a tuple descriptor representing three TEXT columns */
        tupdesc = CreateTemplateTupleDesc(3, false);
        TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                           TEXTOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                           TEXTOID, -1, 0);
        TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
                                           TEXTOID, -1, 0);


        /* prepare for projection of tuples */
        tstate = begin_tup_output_tupdesc(dest, tupdesc);

        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *conf = guc_variables[i];

                if ((conf->flags & GUC_NO_SHOW_ALL) ||
                        ((conf->flags & GUC_SUPERUSER_ONLY) && !am_superuser))
                        continue;

                /* assign to the values array */
                values[0] = (char *) conf->name;
                values[1] = _ShowOption(conf, true);
                values[2] = (char *) conf->short_desc;

                /* send it to dest */
                do_tup_output(tstate, values);

                /* clean up */
                if (values[1] != NULL)
                        pfree(values[1]);
        }

        end_tup_output(tstate);
}

/*
 * Return GUC variable value by name; optionally return canonical
 * form of name.  Return value is palloc'd.
 */
char *
GetConfigOptionByName(const char *name, const char **varname)
{
        struct config_generic *record;

        record = find_option(name, false, ERROR);
        if (record == NULL)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                           errmsg("unrecognized configuration parameter \"%s\"", name)));
        if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
                ereport(ERROR,
                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                 errmsg("must be superuser to examine \"%s\"", name)));

        if (varname)
                *varname = record->name;

        return _ShowOption(record, true);
}

/*
 * Return GUC variable value by variable number; optionally return canonical
 * form of name.  Return value is palloc'd.
 */
void
GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
{
        char            buffer[256];
        struct config_generic *conf;

        /* check requested variable number valid */
        Assert((varnum >= 0) && (varnum < num_guc_variables));

        conf = guc_variables[varnum];

        if (noshow)
        {
                if ((conf->flags & GUC_NO_SHOW_ALL) ||
                        ((conf->flags & GUC_SUPERUSER_ONLY) && !superuser()))
                        *noshow = true;
                else
                        *noshow = false;
        }

        /* first get the generic attributes */

        /* name */
        values[0] = conf->name;

        /* setting : use _ShowOption in order to avoid duplicating the logic */
        values[1] = _ShowOption(conf, false);

        /* unit */
        if (conf->vartype == PGC_INT)
        {
                static char buf[8];

                switch (conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
                {
                        case GUC_UNIT_KB:
                                values[2] = "kB";
                                break;
                        case GUC_UNIT_BLOCKS:
                                snprintf(buf, sizeof(buf), "%dkB", BLCKSZ / 1024);
                                values[2] = buf;
                                break;
                        case GUC_UNIT_XBLOCKS:
                                snprintf(buf, sizeof(buf), "%dkB", XLOG_BLCKSZ / 1024);
                                values[2] = buf;
                                break;
                        case GUC_UNIT_MS:
                                values[2] = "ms";
                                break;
                        case GUC_UNIT_S:
                                values[2] = "s";
                                break;
                        case GUC_UNIT_MIN:
                                values[2] = "min";
                                break;
                        default:
                                values[2] = "";
                                break;
                }
        }
        else
                values[2] = NULL;

        /* group */
        values[3] = config_group_names[conf->group];

        /* short_desc */
        values[4] = conf->short_desc;

        /* extra_desc */
        values[5] = conf->long_desc;

        /* context */
        values[6] = GucContext_Names[conf->context];

        /* vartype */
        values[7] = config_type_names[conf->vartype];

        /* source */
        values[8] = GucSource_Names[conf->source];

        /* now get the type specifc attributes */
        switch (conf->vartype)
        {
                case PGC_BOOL:
                        {
                                struct config_bool *lconf = (struct config_bool *) conf;

                                /* min_val */
                                values[9] = NULL;

                                /* max_val */
                                values[10] = NULL;

                                /* enumvals */
                                values[11] = NULL;

                                /* boot_val */
                                values[12] = pstrdup(lconf->boot_val ? "on" : "off");

                                /* reset_val */
                                values[13] = pstrdup(lconf->reset_val ? "on" : "off");
                        }
                        break;

                case PGC_INT:
                        {
                                struct config_int *lconf = (struct config_int *) conf;

                                /* min_val */
                                snprintf(buffer, sizeof(buffer), "%d", lconf->min);
                                values[9] = pstrdup(buffer);

                                /* max_val */
                                snprintf(buffer, sizeof(buffer), "%d", lconf->max);
                                values[10] = pstrdup(buffer);

                                /* enumvals */
                                values[11] = NULL;

                                /* boot_val */
                                snprintf(buffer, sizeof(buffer), "%d", lconf->boot_val);
                                values[12] = pstrdup(buffer);

                                /* reset_val */
                                snprintf(buffer, sizeof(buffer), "%d", lconf->reset_val);
                                values[13] = pstrdup(buffer);
                        }
                        break;

                case PGC_REAL:
                        {
                                struct config_real *lconf = (struct config_real *) conf;

                                /* min_val */
                                snprintf(buffer, sizeof(buffer), "%g", lconf->min);
                                values[9] = pstrdup(buffer);

                                /* max_val */
                                snprintf(buffer, sizeof(buffer), "%g", lconf->max);
                                values[10] = pstrdup(buffer);

                                /* enumvals */
                                values[11] = NULL;

                                /* boot_val */
                                snprintf(buffer, sizeof(buffer), "%g", lconf->boot_val);
                                values[12] = pstrdup(buffer);

                                /* reset_val */
                                snprintf(buffer, sizeof(buffer), "%g", lconf->reset_val);
                                values[13] = pstrdup(buffer);
                        }
                        break;

                case PGC_STRING:
                        {
                                struct config_string *lconf = (struct config_string *) conf;

                                /* min_val */
                                values[9] = NULL;

                                /* max_val */
                                values[10] = NULL;

                                /* enumvals */
                                values[11] = NULL;

                                /* boot_val */
                                if (lconf->boot_val == NULL)
                                        values[12] = NULL;
                                else
                                        values[12] = pstrdup(lconf->boot_val);

                                /* reset_val */
                                if (lconf->reset_val == NULL)
                                        values[13] = NULL;
                                else
                                        values[13] = pstrdup(lconf->reset_val);
                        }
                        break;

                case PGC_ENUM:
                        {
                                struct config_enum *lconf = (struct config_enum *) conf;

                                /* min_val */
                                values[9] = NULL;

                                /* max_val */
                                values[10] = NULL;

                                /* enumvals */
                                /* NOTE! enumvals with double quotes in them are not supported! */
                                values[11] = config_enum_get_options((struct config_enum *) conf,
                                                                                                         "{\"", "\"}", "\",\"");

                                /* boot_val */
                                values[12] = pstrdup(config_enum_lookup_by_value(lconf,
                                                                                                                                 lconf->boot_val));

                                /* reset_val */
                                values[13] = pstrdup(config_enum_lookup_by_value(lconf,
                                                                                                                                 lconf->reset_val));
                        }
                        break;

                default:
                        {
                                /*
                                 * should never get here, but in case we do, set 'em to NULL
                                 */

                                /* min_val */
                                values[9] = NULL;

                                /* max_val */
                                values[10] = NULL;

                                /* enumvals */
                                values[11] = NULL;

                                /* boot_val */
                                values[12] = NULL;

                                /* reset_val */
                                values[13] = NULL;
                        }
                        break;
        }

        /* 
         * If the setting came from a config file, set the source location.
         * For security reasons, we don't show source file/line number for
         * non-superusers.
         */
        if (conf->source == PGC_S_FILE && superuser())
        {
                values[14] = conf->sourcefile;
                snprintf(buffer, sizeof(buffer), "%d", conf->sourceline);
                values[15] = pstrdup(buffer);
        }
        else
        {
                values[14] = NULL;
                values[15] = NULL;
        }
}

/*
 * Return the total number of GUC variables
 */
int
GetNumConfigOptions(void)
{
        return num_guc_variables;
}

/*
 * show_config_by_name - equiv to SHOW X command but implemented as
 * a function.
 */
Datum
show_config_by_name(PG_FUNCTION_ARGS)
{
        char       *varname;
        char       *varval;

        /* Get the GUC variable name */
        varname = TextDatumGetCString(PG_GETARG_DATUM(0));

        /* Get the value */
        varval = GetConfigOptionByName(varname, NULL);

        /* Convert to text */
        PG_RETURN_TEXT_P(cstring_to_text(varval));
}

/*
 * show_all_settings - equiv to SHOW ALL command but implemented as
 * a Table Function.
 */
#define NUM_PG_SETTINGS_ATTS    16

Datum
show_all_settings(PG_FUNCTION_ARGS)
{
        FuncCallContext *funcctx;
        TupleDesc       tupdesc;
        int                     call_cntr;
        int                     max_calls;
        AttInMetadata *attinmeta;
        MemoryContext oldcontext;

        /* stuff done only on the first call of the function */
        if (SRF_IS_FIRSTCALL())
        {
                /* create a function context for cross-call persistence */
                funcctx = SRF_FIRSTCALL_INIT();

                /*
                 * switch to memory context appropriate for multiple function calls
                 */
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

                /*
                 * need a tuple descriptor representing NUM_PG_SETTINGS_ATTS columns
                 * of the appropriate types
                 */
                tupdesc = CreateTemplateTupleDesc(NUM_PG_SETTINGS_ATTS, false);
                TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 3, "unit",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 4, "category",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 5, "short_desc",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 6, "extra_desc",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 7, "context",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 8, "vartype",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 9, "source",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 10, "min_val",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 11, "max_val",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 12, "enumvals",
                                                   TEXTARRAYOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 13, "boot_val",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 14, "reset_val",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 15, "sourcefile",
                                                   TEXTOID, -1, 0);
                TupleDescInitEntry(tupdesc, (AttrNumber) 16, "sourceline",
                                                   INT4OID, -1, 0);

                /*
                 * Generate attribute metadata needed later to produce tuples from raw
                 * C strings
                 */
                attinmeta = TupleDescGetAttInMetadata(tupdesc);
                funcctx->attinmeta = attinmeta;

                /* total number of tuples to be returned */
                funcctx->max_calls = GetNumConfigOptions();

                MemoryContextSwitchTo(oldcontext);
        }

        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();

        call_cntr = funcctx->call_cntr;
        max_calls = funcctx->max_calls;
        attinmeta = funcctx->attinmeta;

        if (call_cntr < max_calls)      /* do when there is more left to send */
        {
                char       *values[NUM_PG_SETTINGS_ATTS];
                bool            noshow;
                HeapTuple       tuple;
                Datum           result;

                /*
                 * Get the next visible GUC variable name and value
                 */
                do
                {
                        GetConfigOptionByNum(call_cntr, (const char **) values, &noshow);
                        if (noshow)
                        {
                                /* bump the counter and get the next config setting */
                                call_cntr = ++funcctx->call_cntr;

                                /* make sure we haven't gone too far now */
                                if (call_cntr >= max_calls)
                                        SRF_RETURN_DONE(funcctx);
                        }
                } while (noshow);

                /* build a tuple */
                tuple = BuildTupleFromCStrings(attinmeta, values);

                /* make the tuple into a datum */
                result = HeapTupleGetDatum(tuple);

                SRF_RETURN_NEXT(funcctx, result);
        }
        else
        {
                /* do when there is no more left */
                SRF_RETURN_DONE(funcctx);
        }
}

static char *
_ShowOption(struct config_generic * record, bool use_units)
{
        char            buffer[256];
        const char *val;

        switch (record->vartype)
        {
                case PGC_BOOL:
                        {
                                struct config_bool *conf = (struct config_bool *) record;

                                if (conf->show_hook)
                                        val = (*conf->show_hook) ();
                                else
                                        val = *conf->variable ? "on" : "off";
                        }
                        break;

                case PGC_INT:
                        {
                                struct config_int *conf = (struct config_int *) record;

                                if (conf->show_hook)
                                        val = (*conf->show_hook) ();
                                else
                                {
                                        /*
                                         * Use int64 arithmetic to avoid overflows in units
                                         * conversion.  If INT64_IS_BUSTED we might overflow
                                         * anyway and print bogus answers, but there are few
                                         * enough such machines that it doesn't seem worth
                                         * trying harder.
                                         */
                                        int64           result = *conf->variable;
                                        const char *unit;

                                        if (use_units && result > 0 &&
                                                (record->flags & GUC_UNIT_MEMORY))
                                        {
                                                switch (record->flags & GUC_UNIT_MEMORY)
                                                {
                                                        case GUC_UNIT_BLOCKS:
                                                                result *= BLCKSZ / 1024;
                                                                break;
                                                        case GUC_UNIT_XBLOCKS:
                                                                result *= XLOG_BLCKSZ / 1024;
                                                                break;
                                                }

                                                if (result % KB_PER_GB == 0)
                                                {
                                                        result /= KB_PER_GB;
                                                        unit = "GB";
                                                }
                                                else if (result % KB_PER_MB == 0)
                                                {
                                                        result /= KB_PER_MB;
                                                        unit = "MB";
                                                }
                                                else
                                                {
                                                        unit = "kB";
                                                }
                                        }
                                        else if (use_units && result > 0 &&
                                                         (record->flags & GUC_UNIT_TIME))
                                        {
                                                switch (record->flags & GUC_UNIT_TIME)
                                                {
                                                        case GUC_UNIT_S:
                                                                result *= MS_PER_S;
                                                                break;
                                                        case GUC_UNIT_MIN:
                                                                result *= MS_PER_MIN;
                                                                break;
                                                }

                                                if (result % MS_PER_D == 0)
                                                {
                                                        result /= MS_PER_D;
                                                        unit = "d";
                                                }
                                                else if (result % MS_PER_H == 0)
                                                {
                                                        result /= MS_PER_H;
                                                        unit = "h";
                                                }
                                                else if (result % MS_PER_MIN == 0)
                                                {
                                                        result /= MS_PER_MIN;
                                                        unit = "min";
                                                }
                                                else if (result % MS_PER_S == 0)
                                                {
                                                        result /= MS_PER_S;
                                                        unit = "s";
                                                }
                                                else
                                                {
                                                        unit = "ms";
                                                }
                                        }
                                        else
                                                unit = "";

                                        snprintf(buffer, sizeof(buffer), INT64_FORMAT "%s",
                                                         result, unit);
                                        val = buffer;
                                }
                        }
                        break;

                case PGC_REAL:
                        {
                                struct config_real *conf = (struct config_real *) record;

                                if (conf->show_hook)
                                        val = (*conf->show_hook) ();
                                else
                                {
                                        snprintf(buffer, sizeof(buffer), "%g",
                                                         *conf->variable);
                                        val = buffer;
                                }
                        }
                        break;

                case PGC_STRING:
                        {
                                struct config_string *conf = (struct config_string *) record;

                                if (conf->show_hook)
                                        val = (*conf->show_hook) ();
                                else if (*conf->variable && **conf->variable)
                                        val = *conf->variable;
                                else
                                        val = "";
                        }
                        break;

                case PGC_ENUM:
                        {
                                struct config_enum *conf = (struct config_enum *) record;

                                if(conf->show_hook)
                                        val = (*conf->show_hook) ();
                                else
                                        val = config_enum_lookup_by_value(conf, *conf->variable);
                        }
                        break;

                default:
                        /* just to keep compiler quiet */
                        val = "???";
                        break;
        }

        return pstrdup(val);
}


/*
 * Attempt (badly) to detect if a proposed new GUC setting is the same
 * as the current value.
 *
 * XXX this does not really work because it doesn't account for the
 * effects of canonicalization of string values by assign_hooks.
 */
static bool
is_newvalue_equal(struct config_generic * record, const char *newvalue)
{
        /* newvalue == NULL isn't supported */
        Assert(newvalue != NULL);

        switch (record->vartype)
        {
                case PGC_BOOL:
                        {
                                struct config_bool *conf = (struct config_bool *) record;
                                bool            newval;

                                return parse_bool(newvalue, &newval)
                                        && *conf->variable == newval;
                        }
                case PGC_INT:
                        {
                                struct config_int *conf = (struct config_int *) record;
                                int                     newval;

                                return parse_int(newvalue, &newval, record->flags, NULL)
                                        && *conf->variable == newval;
                        }
                case PGC_REAL:
                        {
                                struct config_real *conf = (struct config_real *) record;
                                double          newval;

                                return parse_real(newvalue, &newval)
                                        && *conf->variable == newval;
                        }
                case PGC_STRING:
                        {
                                struct config_string *conf = (struct config_string *) record;

                                return *conf->variable != NULL &&
                                        strcmp(*conf->variable, newvalue) == 0;
                        }

                case PGC_ENUM:
                        {
                                struct config_enum *conf = (struct config_enum *) record;
                                int                     newval;

                                return config_enum_lookup_by_name(conf, newvalue, &newval) &&
                                        *conf->variable == newval;
                        }
        }

        return false;
}


#ifdef EXEC_BACKEND

/*
 *      These routines dump out all non-default GUC options into a binary
 *      file that is read by all exec'ed backends.  The format is:
 *
 *              variable name, string, null terminated
 *              variable value, string, null terminated
 *              variable source, integer
 */
static void
write_one_nondefault_variable(FILE *fp, struct config_generic *gconf)
{
        if (gconf->source == PGC_S_DEFAULT)
                return;

        fprintf(fp, "%s", gconf->name);
        fputc(0, fp);

        switch (gconf->vartype)
        {
                case PGC_BOOL:
                {
                        struct config_bool *conf = (struct config_bool *) gconf;

                        if (*conf->variable)
                                fprintf(fp, "true");
                        else
                                fprintf(fp, "false");
                }
                break;

                case PGC_INT:
                {
                        struct config_int *conf = (struct config_int *) gconf;

                        fprintf(fp, "%d", *conf->variable);
                }
                break;

                case PGC_REAL:
                {
                        struct config_real *conf = (struct config_real *) gconf;

                        /* Could lose precision here? */
                        fprintf(fp, "%f", *conf->variable);
                }
                break;

                case PGC_STRING:
                {
                        struct config_string *conf = (struct config_string *) gconf;

                        fprintf(fp, "%s", *conf->variable);
                }
                break;

                case PGC_ENUM:
                {
                        struct config_enum *conf = (struct config_enum *) gconf;
                                                
                        fprintf(fp, "%s",
                                        config_enum_lookup_by_value(conf, *conf->variable));
                }
                break;
        }

        fputc(0, fp);

        fwrite(&gconf->source, sizeof(gconf->source), 1, fp);
}

void
write_nondefault_variables(GucContext context)
{
        int                     elevel;
        FILE       *fp;
        struct config_generic *cvc_conf;
        int                     i;

        Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);

        elevel = (context == PGC_SIGHUP) ? LOG : ERROR;

        /*
         * Open file
         */
        fp = AllocateFile(CONFIG_EXEC_PARAMS_NEW, "w");
        if (!fp)
        {
                ereport(elevel,
                                (errcode_for_file_access(),
                                 errmsg("could not write to file \"%s\": %m",
                                                CONFIG_EXEC_PARAMS_NEW)));
                return;
        }

        /*
         * custom_variable_classes must be written out first; otherwise we might
         * reject custom variable values while reading the file.
         */
        cvc_conf = find_option("custom_variable_classes", false, ERROR);
        if (cvc_conf)
                write_one_nondefault_variable(fp, cvc_conf);

        for (i = 0; i < num_guc_variables; i++)
        {
                struct config_generic *gconf = guc_variables[i];

                if (gconf != cvc_conf)
                        write_one_nondefault_variable(fp, gconf);
        }

        if (FreeFile(fp))
        {
                ereport(elevel,
                                (errcode_for_file_access(),
                                 errmsg("could not write to file \"%s\": %m",
                                                CONFIG_EXEC_PARAMS_NEW)));
                return;
        }

        /*
         * Put new file in place.  This could delay on Win32, but we don't hold
         * any exclusive locks.
         */
        rename(CONFIG_EXEC_PARAMS_NEW, CONFIG_EXEC_PARAMS);
}


/*
 *      Read string, including null byte from file
 *
 *      Return NULL on EOF and nothing read
 */
static char *
read_string_with_null(FILE *fp)
{
        int                     i = 0,
                                ch,
                                maxlen = 256;
        char       *str = NULL;

        do
        {
                if ((ch = fgetc(fp)) == EOF)
                {
                        if (i == 0)
                                return NULL;
                        else
                                elog(FATAL, "invalid format of exec config params file");
                }
                if (i == 0)
                        str = guc_malloc(FATAL, maxlen);
                else if (i == maxlen)
                        str = guc_realloc(FATAL, str, maxlen *= 2);
                str[i++] = ch;
        } while (ch != 0);

        return str;
}


/*
 *      This routine loads a previous postmaster dump of its non-default
 *      settings.
 */
void
read_nondefault_variables(void)
{
        FILE       *fp;
        char       *varname,
                           *varvalue;
        int                     varsource;

        /*
         * Open file
         */
        fp = AllocateFile(CONFIG_EXEC_PARAMS, "r");
        if (!fp)
        {
                /* File not found is fine */
                if (errno != ENOENT)
                        ereport(FATAL,
                                        (errcode_for_file_access(),
                                         errmsg("could not read from file \"%s\": %m",
                                                        CONFIG_EXEC_PARAMS)));
                return;
        }

        for (;;)
        {
                struct config_generic *record;

                if ((varname = read_string_with_null(fp)) == NULL)
                        break;

                if ((record = find_option(varname, true, FATAL)) == NULL)
                        elog(FATAL, "failed to locate variable %s in exec config params file", varname);
                if ((varvalue = read_string_with_null(fp)) == NULL)
                        elog(FATAL, "invalid format of exec config params file");
                if (fread(&varsource, sizeof(varsource), 1, fp) == 0)
                        elog(FATAL, "invalid format of exec config params file");

                (void) set_config_option(varname, varvalue, record->context,
                                                                 varsource, GUC_ACTION_SET, true);
                free(varname);
                free(varvalue);
        }

        FreeFile(fp);
}
#endif   /* EXEC_BACKEND */


/*
 * A little "long argument" simulation, although not quite GNU
 * compliant. Takes a string of the form "some-option=some value" and
 * returns name = "some_option" and value = "some value" in malloc'ed
 * storage. Note that '-' is converted to '_' in the option name. If
 * there is no '=' in the input string then value will be NULL.
 */
void
ParseLongOption(const char *string, char **name, char **value)
{
        size_t          equal_pos;
        char       *cp;

        AssertArg(string);
        AssertArg(name);
        AssertArg(value);

        equal_pos = strcspn(string, "=");

        if (string[equal_pos] == '=')
        {
                *name = guc_malloc(FATAL, equal_pos + 1);
                strlcpy(*name, string, equal_pos + 1);

                *value = guc_strdup(FATAL, &string[equal_pos + 1]);
        }
        else
        {
                /* no equal sign in string */
                *name = guc_strdup(FATAL, string);
                *value = NULL;
        }

        for (cp = *name; *cp; cp++)
                if (*cp == '-')
                        *cp = '_';
}


/*
 * Handle options fetched from pg_database.datconfig, pg_authid.rolconfig,
 * pg_proc.proconfig, etc.      Caller must specify proper context/source/action.
 *
 * The array parameter must be an array of TEXT (it must not be NULL).
 */
void
ProcessGUCArray(ArrayType *array,
                                GucContext context, GucSource source, GucAction action)
{
        int                     i;

        Assert(array != NULL);
        Assert(ARR_ELEMTYPE(array) == TEXTOID);
        Assert(ARR_NDIM(array) == 1);
        Assert(ARR_LBOUND(array)[0] == 1);

        for (i = 1; i <= ARR_DIMS(array)[0]; i++)
        {
                Datum           d;
                bool            isnull;
                char       *s;
                char       *name;
                char       *value;

                d = array_ref(array, 1, &i,
                                          -1 /* varlenarray */ ,
                                          -1 /* TEXT's typlen */ ,
                                          false /* TEXT's typbyval */ ,
                                          'i' /* TEXT's typalign */ ,
                                          &isnull);

                if (isnull)
                        continue;

                s = TextDatumGetCString(d);

                ParseLongOption(s, &name, &value);
                if (!value)
                {
                        ereport(WARNING,
                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                         errmsg("could not parse setting for parameter \"%s\"",
                                                        name)));
                        free(name);
                        continue;
                }

                (void) set_config_option(name, value, context, source, action, true);

                free(name);
                if (value)
                        free(value);
        }
}


/*
 * Add an entry to an option array.  The array parameter may be NULL
 * to indicate the current table entry is NULL.
 */
ArrayType *
GUCArrayAdd(ArrayType *array, const char *name, const char *value)
{
        const char *varname;
        Datum           datum;
        char       *newval;
        ArrayType  *a;

        Assert(name);
        Assert(value);

        /* test if the option is valid */
        set_config_option(name, value,
                                          superuser() ? PGC_SUSET : PGC_USERSET,
                                          PGC_S_TEST, GUC_ACTION_SET, false);

        /* convert name to canonical spelling, so we can use plain strcmp */
        (void) GetConfigOptionByName(name, &varname);
        name = varname;

        newval = palloc(strlen(name) + 1 + strlen(value) + 1);
        sprintf(newval, "%s=%s", name, value);
        datum = CStringGetTextDatum(newval);

        if (array)
        {
                int                     index;
                bool            isnull;
                int                     i;

                Assert(ARR_ELEMTYPE(array) == TEXTOID);
                Assert(ARR_NDIM(array) == 1);
                Assert(ARR_LBOUND(array)[0] == 1);

                index = ARR_DIMS(array)[0] + 1; /* add after end */

                for (i = 1; i <= ARR_DIMS(array)[0]; i++)
                {
                        Datum           d;
                        char       *current;

                        d = array_ref(array, 1, &i,
                                                  -1 /* varlenarray */ ,
                                                  -1 /* TEXT's typlen */ ,
                                                  false /* TEXT's typbyval */ ,
                                                  'i' /* TEXT's typalign */ ,
                                                  &isnull);
                        if (isnull)
                                continue;
                        current = TextDatumGetCString(d);
                        if (strncmp(current, newval, strlen(name) + 1) == 0)
                        {
                                index = i;
                                break;
                        }
                }

                a = array_set(array, 1, &index,
                                          datum,
                                          false,
                                          -1 /* varlena array */ ,
                                          -1 /* TEXT's typlen */ ,
                                          false /* TEXT's typbyval */ ,
                                          'i' /* TEXT's typalign */ );
        }
        else
                a = construct_array(&datum, 1,
                                                        TEXTOID,
                                                        -1, false, 'i');

        return a;
}


/*
 * Delete an entry from an option array.  The array parameter may be NULL
 * to indicate the current table entry is NULL.  Also, if the return value
 * is NULL then a null should be stored.
 */
ArrayType *
GUCArrayDelete(ArrayType *array, const char *name)
{
        const char *varname;
        ArrayType  *newarray;
        int                     i;
        int                     index;

        Assert(name);

        /* test if the option is valid */
        set_config_option(name, NULL,
                                          superuser() ? PGC_SUSET : PGC_USERSET,
                                          PGC_S_TEST, GUC_ACTION_SET, false);

        /* convert name to canonical spelling, so we can use plain strcmp */
        (void) GetConfigOptionByName(name, &varname);
        name = varname;

        /* if array is currently null, then surely nothing to delete */
        if (!array)
                return NULL;

        newarray = NULL;
        index = 1;

        for (i = 1; i <= ARR_DIMS(array)[0]; i++)
        {
                Datum           d;
                char       *val;
                bool            isnull;

                d = array_ref(array, 1, &i,
                                          -1 /* varlenarray */ ,
                                          -1 /* TEXT's typlen */ ,
                                          false /* TEXT's typbyval */ ,
                                          'i' /* TEXT's typalign */ ,
                                          &isnull);
                if (isnull)
                        continue;
                val = TextDatumGetCString(d);

                /* ignore entry if it's what we want to delete */
                if (strncmp(val, name, strlen(name)) == 0
                        && val[strlen(name)] == '=')
                        continue;

                /* else add it to the output array */
                if (newarray)
                {
                        newarray = array_set(newarray, 1, &index,
                                                                 d,
                                                                 false,
                                                                 -1 /* varlenarray */ ,
                                                                 -1 /* TEXT's typlen */ ,
                                                                 false /* TEXT's typbyval */ ,
                                                                 'i' /* TEXT's typalign */ );
                }
                else
                        newarray = construct_array(&d, 1,
                                                                           TEXTOID,
                                                                           -1, false, 'i');

                index++;
        }

        return newarray;
}


/*
 * assign_hook and show_hook subroutines
 */

static const char *
assign_log_destination(const char *value, bool doit, GucSource source)
{
        char       *rawstring;
        List       *elemlist;
        ListCell   *l;
        int                     newlogdest = 0;

        /* Need a modifiable copy of string */
        rawstring = pstrdup(value);

        /* Parse string into list of identifiers */
        if (!SplitIdentifierString(rawstring, ',', &elemlist))
        {
                /* syntax error in list */
                pfree(rawstring);
                list_free(elemlist);
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                        errmsg("invalid list syntax for parameter \"log_destination\"")));
                return NULL;
        }

        foreach(l, elemlist)
        {
                char       *tok = (char *) lfirst(l);

                if (pg_strcasecmp(tok, "stderr") == 0)
                        newlogdest |= LOG_DESTINATION_STDERR;
                else if (pg_strcasecmp(tok, "csvlog") == 0)
                        newlogdest |= LOG_DESTINATION_CSVLOG;
#ifdef HAVE_SYSLOG
                else if (pg_strcasecmp(tok, "syslog") == 0)
                        newlogdest |= LOG_DESTINATION_SYSLOG;
#endif
#ifdef WIN32
                else if (pg_strcasecmp(tok, "eventlog") == 0)
                        newlogdest |= LOG_DESTINATION_EVENTLOG;
#endif
                else
                {
                        ereport(GUC_complaint_elevel(source),
                                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                  errmsg("unrecognized \"log_destination\" key word: \"%s\"",
                                                 tok)));
                        pfree(rawstring);
                        list_free(elemlist);
                        return NULL;
                }
        }

        if (doit)
                Log_destination = newlogdest;

        pfree(rawstring);
        list_free(elemlist);

        return value;
}

#ifdef HAVE_SYSLOG

static bool
assign_syslog_facility(int newval, bool doit, GucSource source)
{
        if (doit)
                set_syslog_parameters(syslog_ident_str ? syslog_ident_str : "postgres",
                                                          newval);

        return true;
}

static const char *
assign_syslog_ident(const char *ident, bool doit, GucSource source)
{
        if (doit)
                set_syslog_parameters(ident, syslog_facility);

        return ident;
}
#endif   /* HAVE_SYSLOG */


static bool
assign_session_replication_role(int newval, bool doit, GucSource source)
{
        /*
         * Must flush the plan cache when changing replication role; but don't
         * flush unnecessarily.
         */
        if (doit && SessionReplicationRole != newval)
        {
                ResetPlanCache();
        }

        return true;
}

static const char *
show_num_temp_buffers(void)
{
        /*
         * We show the GUC var until local buffers have been initialized, and
         * NLocBuffer afterwards.
         */
        static char nbuf[32];

        sprintf(nbuf, "%d", NLocBuffer ? NLocBuffer : num_temp_buffers);
        return nbuf;
}

static bool
assign_phony_autocommit(bool newval, bool doit, GucSource source)
{
        if (!newval)
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("SET AUTOCOMMIT TO OFF is no longer supported")));
                return false;
        }
        return true;
}

static const char *
assign_custom_variable_classes(const char *newval, bool doit, GucSource source)
{
        /*
         * Check syntax. newval must be a comma separated list of identifiers.
         * Whitespace is allowed but removed from the result.
         */
        bool            hasSpaceAfterToken = false;
        const char *cp = newval;
        int                     symLen = 0;
        char            c;
        StringInfoData buf;

        initStringInfo(&buf);
        while ((c = *cp++) != '\0')
        {
                if (isspace((unsigned char) c))
                {
                        if (symLen > 0)
                                hasSpaceAfterToken = true;
                        continue;
                }

                if (c == ',')
                {
                        if (symLen > 0)         /* terminate identifier */
                        {
                                appendStringInfoChar(&buf, ',');
                                symLen = 0;
                        }
                        hasSpaceAfterToken = false;
                        continue;
                }

                if (hasSpaceAfterToken || !(isalnum((unsigned char) c) || c == '_'))
                {
                        /*
                         * Syntax error due to token following space after token or
                         * non-identifier character
                         */
                        pfree(buf.data);
                        return NULL;
                }
                appendStringInfoChar(&buf, c);
                symLen++;
        }

        /* Remove stray ',' at end */
        if (symLen == 0 && buf.len > 0)
                buf.data[--buf.len] = '\0';

        /* GUC wants the result malloc'd */
        newval = guc_strdup(LOG, buf.data);

        pfree(buf.data);
        return newval;
}

static bool
assign_debug_assertions(bool newval, bool doit, GucSource source)
{
#ifndef USE_ASSERT_CHECKING
        if (newval)
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                           errmsg("assertion checking is not supported by this build")));
                return false;
        }
#endif
        return true;
}

static bool
assign_ssl(bool newval, bool doit, GucSource source)
{
#ifndef USE_SSL
        if (newval)
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("SSL is not supported by this build")));
                return false;
        }
#endif
        return true;
}

static bool
assign_stage_log_stats(bool newval, bool doit, GucSource source)
{
        if (newval && log_statement_stats)
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("cannot enable parameter when \"log_statement_stats\" is true")));
                /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
                if (source != PGC_S_OVERRIDE)
                        return false;
        }
        return true;
}

static bool
assign_log_stats(bool newval, bool doit, GucSource source)
{
        if (newval &&
                (log_parser_stats || log_planner_stats || log_executor_stats))
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("cannot enable \"log_statement_stats\" when "
                                                "\"log_parser_stats\", \"log_planner_stats\", "
                                                "or \"log_executor_stats\" is true")));
                /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
                if (source != PGC_S_OVERRIDE)
                        return false;
        }
        return true;
}

static bool
assign_transaction_read_only(bool newval, bool doit, GucSource source)
{
        /* Can't go to r/w mode inside a r/o transaction */
        if (newval == false && XactReadOnly && IsSubTransaction())
        {
                ereport(GUC_complaint_elevel(source),
                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                 errmsg("cannot set transaction read-write mode inside a read-only transaction")));
                /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
                if (source != PGC_S_OVERRIDE)
                        return false;
        }
        return true;
}

static const char *
assign_canonical_path(const char *newval, bool doit, GucSource source)
{
        if (doit)
        {
                char       *canon_val = guc_strdup(ERROR, newval);

                canonicalize_path(canon_val);
                return canon_val;
        }
        else
                return newval;
}

static const char *
assign_timezone_abbreviations(const char *newval, bool doit, GucSource source)
{
        /*
         * The powerup value shown above for timezone_abbreviations is "UNKNOWN".
         * When we see this we just do nothing.  If this value isn't overridden
         * from the config file then pg_timezone_abbrev_initialize() will
         * eventually replace it with "Default".  This hack has two purposes: to
         * avoid wasting cycles loading values that might soon be overridden from
         * the config file, and to avoid trying to read the timezone abbrev files
         * during InitializeGUCOptions().  The latter doesn't work in an
         * EXEC_BACKEND subprocess because my_exec_path hasn't been set yet and so
         * we can't locate PGSHAREDIR.  (Essentially the same hack is used to
         * delay initializing TimeZone ... if we have any more, we should try to
         * clean up and centralize this mechanism ...)
         */
        if (strcmp(newval, "UNKNOWN") == 0)
        {
                return newval;
        }

        /* Loading abbrev file is expensive, so only do it when value changes */
        if (timezone_abbreviations_string == NULL ||
                strcmp(timezone_abbreviations_string, newval) != 0)
        {
                int                     elevel;

                /*
                 * If reading config file, only the postmaster should bleat loudly
                 * about problems.      Otherwise, it's just this one process doing it,
                 * and we use WARNING message level.
                 */
                if (source == PGC_S_FILE)
                        elevel = IsUnderPostmaster ? DEBUG3 : LOG;
                else
                        elevel = WARNING;
                if (!load_tzoffsets(newval, doit, elevel))
                        return NULL;
        }
        return newval;
}

/*
 * pg_timezone_abbrev_initialize --- set default value if not done already
 *
 * This is called after initial loading of postgresql.conf.  If no
 * timezone_abbreviations setting was found therein, select default.
 */
void
pg_timezone_abbrev_initialize(void)
{
        if (strcmp(timezone_abbreviations_string, "UNKNOWN") == 0)
        {
                SetConfigOption("timezone_abbreviations", "Default",
                                                PGC_POSTMASTER, PGC_S_ARGV);
        }
}

static const char *
show_archive_command(void)
{
        if (XLogArchiveMode)
                return XLogArchiveCommand;
        else
                return "(disabled)";
}

static bool
assign_tcp_keepalives_idle(int newval, bool doit, GucSource source)
{
        if (doit)
                return (pq_setkeepalivesidle(newval, MyProcPort) == STATUS_OK);

        return true;
}

static const char *
show_tcp_keepalives_idle(void)
{
        static char nbuf[16];

        snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesidle(MyProcPort));
        return nbuf;
}

static bool
assign_tcp_keepalives_interval(int newval, bool doit, GucSource source)
{
        if (doit)
                return (pq_setkeepalivesinterval(newval, MyProcPort) == STATUS_OK);

        return true;
}

static const char *
show_tcp_keepalives_interval(void)
{
        static char nbuf[16];

        snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesinterval(MyProcPort));
        return nbuf;
}

static bool
assign_tcp_keepalives_count(int newval, bool doit, GucSource source)
{
        if (doit)
                return (pq_setkeepalivescount(newval, MyProcPort) == STATUS_OK);

        return true;
}

static const char *
show_tcp_keepalives_count(void)
{
        static char nbuf[16];

        snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivescount(MyProcPort));
        return nbuf;
}

static bool
assign_maxconnections(int newval, bool doit, GucSource source)
{
        if (newval + autovacuum_max_workers > INT_MAX / 4)
                return false;

        if (doit)
                MaxBackends = newval + autovacuum_max_workers;

        return true;
}

static bool
assign_autovacuum_max_workers(int newval, bool doit, GucSource source)
{
        if (newval + MaxConnections > INT_MAX / 4)
                return false;

        if (doit)
                MaxBackends = newval + MaxConnections;

        return true;
}

static bool
assign_effective_io_concurrency(int newval, bool doit, GucSource source)
{
#ifdef USE_PREFETCH
        double          new_prefetch_pages = 0.0;
        int                     i;

        /*----------
         * The user-visible GUC parameter is the number of drives (spindles),
         * which we need to translate to a number-of-pages-to-prefetch target.
         *
         * The expected number of prefetch pages needed to keep N drives busy is:
         *
         * drives |   I/O requests
         * -------+----------------
         *      1 |   1
         *      2 |   2/1 + 2/2 = 3
         *      3 |   3/1 + 3/2 + 3/3 = 5 1/2
         *      4 |   4/1 + 4/2 + 4/3 + 4/4 = 8 1/3
         *      n |   n * H(n)
         *
         * This is called the "coupon collector problem" and H(n) is called the
         * harmonic series.  This could be approximated by n * ln(n), but for
         * reasonable numbers of drives we might as well just compute the series.
         *
         * Alternatively we could set the target to the number of pages necessary
         * so that the expected number of active spindles is some arbitrary
         * percentage of the total.  This sounds the same but is actually slightly
         * different.  The result ends up being ln(1-P)/ln((n-1)/n) where P is
         * that desired fraction.
         *
         * Experimental results show that both of these formulas aren't aggressive
         * enough, but we don't really have any better proposals.
         *
         * Note that if newval = 0 (disabled), we must set target = 0.
         *----------
         */

        for (i = 1; i <= newval; i++)
                new_prefetch_pages += (double) newval / (double) i;

        /* This range check shouldn't fail, but let's be paranoid */
        if (new_prefetch_pages >= 0.0 && new_prefetch_pages < (double) INT_MAX)
        {
                if (doit)
                        target_prefetch_pages = (int) rint(new_prefetch_pages);
                return true;
        }
        else
                return false;
#else
        return true;
#endif /* USE_PREFETCH */
}

static const char *
assign_pgstat_temp_directory(const char *newval, bool doit, GucSource source)
{
        if (doit)
        {
                if (pgstat_stat_tmpname)
                        free(pgstat_stat_tmpname);
                if (pgstat_stat_filename)
                        free(pgstat_stat_filename);

                pgstat_stat_tmpname = guc_malloc(FATAL, strlen(newval) + 12);  /* /pgstat.tmp */
                pgstat_stat_filename = guc_malloc(FATAL, strlen(newval) + 13); /* /pgstat.stat */

                sprintf(pgstat_stat_tmpname, "%s/pgstat.tmp", newval);
                sprintf(pgstat_stat_filename, "%s/pgstat.stat", newval);
        }

        return newval;
}

#include "guc-file.c"