Add support for incremental backup.

[pgsql.git] / src / bin / pg_resetwal / pg_resetwal.c

/*-------------------------------------------------------------------------
 *
 * pg_resetwal.c
 *        A utility to "zero out" the xlog when it's corrupt beyond recovery.
 *        Can also rebuild pg_control if needed.
 *
 * The theory of operation is fairly simple:
 *        1. Read the existing pg_control (which will include the last
 *               checkpoint record).
 *        2. If pg_control is corrupt, attempt to intuit reasonable values,
 *               by scanning the old xlog if necessary.
 *        3. Modify pg_control to reflect a "shutdown" state with a checkpoint
 *               record at the start of xlog.
 *        4. Flush the existing xlog files and write a new segment with
 *               just a checkpoint record in it.  The new segment is positioned
 *               just past the end of the old xlog, so that existing LSNs in
 *               data pages will appear to be "in the past".
 * This is all pretty straightforward except for the intuition part of
 * step 2 ...
 *
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/pg_resetwal/pg_resetwal.c
 *
 *-------------------------------------------------------------------------
 */

/*
 * We have to use postgres.h not postgres_fe.h here, because there's so much
 * backend-only stuff in the XLOG include files we need.  But we need a
 * frontend-ish environment otherwise.  Hence this ugly hack.
 */
#define FRONTEND 1

#include "postgres.h"

#include <dirent.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>

#include "access/heaptoast.h"
#include "access/multixact.h"
#include "access/transam.h"
#include "access/xlog.h"
#include "access/xlog_internal.h"
#include "common/controldata_utils.h"
#include "common/fe_memutils.h"
#include "common/file_perm.h"
#include "common/logging.h"
#include "common/restricted_token.h"
#include "common/string.h"
#include "fe_utils/option_utils.h"
#include "getopt_long.h"
#include "pg_getopt.h"
#include "storage/large_object.h"

static ControlFileData ControlFile; /* pg_control values */
static XLogSegNo newXlogSegNo;  /* new XLOG segment # */
static bool guessed = false;    /* T if we had to guess at any values */
static const char *progname;
static uint32 set_xid_epoch = (uint32) -1;
static TransactionId set_oldest_xid = 0;
static TransactionId set_xid = 0;
static TransactionId set_oldest_commit_ts_xid = 0;
static TransactionId set_newest_commit_ts_xid = 0;
static Oid      set_oid = 0;
static MultiXactId set_mxid = 0;
static MultiXactOffset set_mxoff = (MultiXactOffset) -1;
static TimeLineID minXlogTli = 0;
static XLogSegNo minXlogSegNo = 0;
static int      WalSegSz;
static int      set_wal_segsize;

static void CheckDataVersion(void);
static bool read_controlfile(void);
static void GuessControlValues(void);
static void PrintControlValues(bool guessed);
static void PrintNewControlValues(void);
static void RewriteControlFile(void);
static void FindEndOfXLOG(void);
static void KillExistingXLOG(void);
static void KillExistingArchiveStatus(void);
static void KillExistingWALSummaries(void);
static void WriteEmptyXLOG(void);
static void usage(void);


int
main(int argc, char *argv[])
{
        static struct option long_options[] = {
                {"commit-timestamp-ids", required_argument, NULL, 'c'},
                {"pgdata", required_argument, NULL, 'D'},
                {"epoch", required_argument, NULL, 'e'},
                {"force", no_argument, NULL, 'f'},
                {"next-wal-file", required_argument, NULL, 'l'},
                {"multixact-ids", required_argument, NULL, 'm'},
                {"dry-run", no_argument, NULL, 'n'},
                {"next-oid", required_argument, NULL, 'o'},
                {"multixact-offset", required_argument, NULL, 'O'},
                {"oldest-transaction-id", required_argument, NULL, 'u'},
                {"next-transaction-id", required_argument, NULL, 'x'},
                {"wal-segsize", required_argument, NULL, 1},
                {NULL, 0, NULL, 0}
        };

        int                     c;
        bool            force = false;
        bool            noupdate = false;
        MultiXactId set_oldestmxid = 0;
        char       *endptr;
        char       *endptr2;
        char       *DataDir = NULL;
        char       *log_fname = NULL;
        int                     fd;

        pg_logging_init(argv[0]);
        set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_resetwal"));
        progname = get_progname(argv[0]);

        if (argc > 1)
        {
                if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
                {
                        usage();
                        exit(0);
                }
                if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
                {
                        puts("pg_resetwal (PostgreSQL) " PG_VERSION);
                        exit(0);
                }
        }


        while ((c = getopt_long(argc, argv, "c:D:e:fl:m:no:O:u:x:", long_options, NULL)) != -1)
        {
                switch (c)
                {
                        case 'D':
                                DataDir = optarg;
                                break;

                        case 'f':
                                force = true;
                                break;

                        case 'n':
                                noupdate = true;
                                break;

                        case 'e':
                                errno = 0;
                                set_xid_epoch = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != '\0' || errno != 0)
                                {
                                        /*------
                                          translator: the second %s is a command line argument (-e, etc) */
                                        pg_log_error("invalid argument for option %s", "-e");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (set_xid_epoch == -1)
                                        pg_fatal("transaction ID epoch (-e) must not be -1");
                                break;

                        case 'u':
                                errno = 0;
                                set_oldest_xid = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-u");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (!TransactionIdIsNormal(set_oldest_xid))
                                        pg_fatal("oldest transaction ID (-u) must be greater than or equal to %u", FirstNormalTransactionId);
                                break;

                        case 'x':
                                errno = 0;
                                set_xid = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-x");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (!TransactionIdIsNormal(set_xid))
                                        pg_fatal("transaction ID (-x) must be greater than or equal to %u", FirstNormalTransactionId);
                                break;

                        case 'c':
                                errno = 0;
                                set_oldest_commit_ts_xid = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != ',' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-c");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                set_newest_commit_ts_xid = strtoul(endptr + 1, &endptr2, 0);
                                if (endptr2 == endptr + 1 || *endptr2 != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-c");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }

                                if (set_oldest_commit_ts_xid < FirstNormalTransactionId &&
                                        set_oldest_commit_ts_xid != InvalidTransactionId)
                                        pg_fatal("transaction ID (-c) must be either %u or greater than or equal to %u", InvalidTransactionId, FirstNormalTransactionId);

                                if (set_newest_commit_ts_xid < FirstNormalTransactionId &&
                                        set_newest_commit_ts_xid != InvalidTransactionId)
                                        pg_fatal("transaction ID (-c) must be either %u or greater than or equal to %u", InvalidTransactionId, FirstNormalTransactionId);
                                break;

                        case 'o':
                                errno = 0;
                                set_oid = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-o");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (set_oid == 0)
                                        pg_fatal("OID (-o) must not be 0");
                                break;

                        case 'm':
                                errno = 0;
                                set_mxid = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != ',' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-m");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }

                                set_oldestmxid = strtoul(endptr + 1, &endptr2, 0);
                                if (endptr2 == endptr + 1 || *endptr2 != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-m");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (set_mxid == 0)
                                        pg_fatal("multitransaction ID (-m) must not be 0");

                                /*
                                 * XXX It'd be nice to have more sanity checks here, e.g. so
                                 * that oldest is not wrapped around w.r.t. nextMulti.
                                 */
                                if (set_oldestmxid == 0)
                                        pg_fatal("oldest multitransaction ID (-m) must not be 0");
                                break;

                        case 'O':
                                errno = 0;
                                set_mxoff = strtoul(optarg, &endptr, 0);
                                if (endptr == optarg || *endptr != '\0' || errno != 0)
                                {
                                        pg_log_error("invalid argument for option %s", "-O");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }
                                if (set_mxoff == -1)
                                        pg_fatal("multitransaction offset (-O) must not be -1");
                                break;

                        case 'l':
                                if (strspn(optarg, "01234567890ABCDEFabcdef") != XLOG_FNAME_LEN)
                                {
                                        pg_log_error("invalid argument for option %s", "-l");
                                        pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                        exit(1);
                                }

                                /*
                                 * XLogFromFileName requires wal segment size which is not yet
                                 * set. Hence wal details are set later on.
                                 */
                                log_fname = pg_strdup(optarg);
                                break;

                        case 1:
                                {
                                        int                     wal_segsize_mb;

                                        if (!option_parse_int(optarg, "--wal-segsize", 1, 1024, &wal_segsize_mb))
                                                exit(1);
                                        set_wal_segsize = wal_segsize_mb * 1024 * 1024;
                                        if (!IsValidWalSegSize(set_wal_segsize))
                                                pg_fatal("argument of %s must be a power of two between 1 and 1024", "--wal-segsize");
                                        break;
                                }

                        default:
                                /* getopt_long already emitted a complaint */
                                pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                                exit(1);
                }
        }

        if (DataDir == NULL && optind < argc)
                DataDir = argv[optind++];

        /* Complain if any arguments remain */
        if (optind < argc)
        {
                pg_log_error("too many command-line arguments (first is \"%s\")",
                                         argv[optind]);
                pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                exit(1);
        }

        if (DataDir == NULL)
        {
                pg_log_error("no data directory specified");
                pg_log_error_hint("Try \"%s --help\" for more information.", progname);
                exit(1);
        }

        /*
         * Don't allow pg_resetwal to be run as root, to avoid overwriting the
         * ownership of files in the data directory. We need only check for root
         * -- any other user won't have sufficient permissions to modify files in
         * the data directory.
         */
#ifndef WIN32
        if (geteuid() == 0)
        {
                pg_log_error("cannot be executed by \"root\"");
                pg_log_error_hint("You must run %s as the PostgreSQL superuser.",
                                                  progname);
                exit(1);
        }
#endif

        get_restricted_token();

        /* Set mask based on PGDATA permissions */
        if (!GetDataDirectoryCreatePerm(DataDir))
                pg_fatal("could not read permissions of directory \"%s\": %m",
                                 DataDir);

        umask(pg_mode_mask);

        if (chdir(DataDir) < 0)
                pg_fatal("could not change directory to \"%s\": %m",
                                 DataDir);

        /* Check that data directory matches our server version */
        CheckDataVersion();

        /*
         * Check for a postmaster lock file --- if there is one, refuse to
         * proceed, on grounds we might be interfering with a live installation.
         */
        if ((fd = open("postmaster.pid", O_RDONLY, 0)) < 0)
        {
                if (errno != ENOENT)
                        pg_fatal("could not open file \"%s\" for reading: %m",
                                         "postmaster.pid");
        }
        else
        {
                pg_log_error("lock file \"%s\" exists", "postmaster.pid");
                pg_log_error_hint("Is a server running?  If not, delete the lock file and try again.");
                exit(1);
        }

        /*
         * Attempt to read the existing pg_control file
         */
        if (!read_controlfile())
                GuessControlValues();

        /*
         * If no new WAL segment size was specified, use the control file value.
         */
        if (set_wal_segsize != 0)
                WalSegSz = set_wal_segsize;
        else
                WalSegSz = ControlFile.xlog_seg_size;

        if (log_fname != NULL)
                XLogFromFileName(log_fname, &minXlogTli, &minXlogSegNo, WalSegSz);

        /*
         * Also look at existing segment files to set up newXlogSegNo
         */
        FindEndOfXLOG();

        /*
         * If we're not going to proceed with the reset, print the current control
         * file parameters.
         */
        if ((guessed && !force) || noupdate)
                PrintControlValues(guessed);

        /*
         * Adjust fields if required by switches.  (Do this now so that printout,
         * if any, includes these values.)
         */
        if (set_xid_epoch != -1)
                ControlFile.checkPointCopy.nextXid =
                        FullTransactionIdFromEpochAndXid(set_xid_epoch,
                                                                                         XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));

        if (set_oldest_xid != 0)
        {
                ControlFile.checkPointCopy.oldestXid = set_oldest_xid;
                ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
        }

        if (set_xid != 0)
                ControlFile.checkPointCopy.nextXid =
                        FullTransactionIdFromEpochAndXid(EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid),
                                                                                         set_xid);

        if (set_oldest_commit_ts_xid != 0)
                ControlFile.checkPointCopy.oldestCommitTsXid = set_oldest_commit_ts_xid;
        if (set_newest_commit_ts_xid != 0)
                ControlFile.checkPointCopy.newestCommitTsXid = set_newest_commit_ts_xid;

        if (set_oid != 0)
                ControlFile.checkPointCopy.nextOid = set_oid;

        if (set_mxid != 0)
        {
                ControlFile.checkPointCopy.nextMulti = set_mxid;

                ControlFile.checkPointCopy.oldestMulti = set_oldestmxid;
                if (ControlFile.checkPointCopy.oldestMulti < FirstMultiXactId)
                        ControlFile.checkPointCopy.oldestMulti += FirstMultiXactId;
                ControlFile.checkPointCopy.oldestMultiDB = InvalidOid;
        }

        if (set_mxoff != -1)
                ControlFile.checkPointCopy.nextMultiOffset = set_mxoff;

        if (minXlogTli > ControlFile.checkPointCopy.ThisTimeLineID)
        {
                ControlFile.checkPointCopy.ThisTimeLineID = minXlogTli;
                ControlFile.checkPointCopy.PrevTimeLineID = minXlogTli;
        }

        if (set_wal_segsize != 0)
                ControlFile.xlog_seg_size = WalSegSz;

        if (minXlogSegNo > newXlogSegNo)
                newXlogSegNo = minXlogSegNo;

        if (noupdate)
        {
                PrintNewControlValues();
                exit(0);
        }

        /*
         * If we had to guess anything, and -f was not given, just print the
         * guessed values and exit.
         */
        if (guessed && !force)
        {
                PrintNewControlValues();
                pg_log_error("not proceeding because control file values were guessed");
                pg_log_error_hint("If these values seem acceptable, use -f to force reset.");
                exit(1);
        }

        /*
         * Don't reset from a dirty pg_control without -f, either.
         */
        if (ControlFile.state != DB_SHUTDOWNED && !force)
        {
                pg_log_error("database server was not shut down cleanly");
                pg_log_error_detail("Resetting the write-ahead log might cause data to be lost.");
                pg_log_error_hint("If you want to proceed anyway, use -f to force reset.");
                exit(1);
        }

        /*
         * Else, do the dirty deed.
         */
        RewriteControlFile();
        KillExistingXLOG();
        KillExistingArchiveStatus();
        KillExistingWALSummaries();
        WriteEmptyXLOG();

        printf(_("Write-ahead log reset\n"));
        return 0;
}


/*
 * Look at the version string stored in PG_VERSION and decide if this utility
 * can be run safely or not.
 *
 * We don't want to inject pg_control and WAL files that are for a different
 * major version; that can't do anything good.  Note that we don't treat
 * mismatching version info in pg_control as a reason to bail out, because
 * recovering from a corrupted pg_control is one of the main reasons for this
 * program to exist at all.  However, PG_VERSION is unlikely to get corrupted,
 * and if it were it would be easy to fix by hand.  So let's make this check
 * to prevent simple user errors.
 */
static void
CheckDataVersion(void)
{
        const char *ver_file = "PG_VERSION";
        FILE       *ver_fd;
        char            rawline[64];

        if ((ver_fd = fopen(ver_file, "r")) == NULL)
                pg_fatal("could not open file \"%s\" for reading: %m",
                                 ver_file);

        /* version number has to be the first line read */
        if (!fgets(rawline, sizeof(rawline), ver_fd))
        {
                if (!ferror(ver_fd))
                        pg_fatal("unexpected empty file \"%s\"", ver_file);
                else
                        pg_fatal("could not read file \"%s\": %m", ver_file);
        }

        /* strip trailing newline and carriage return */
        (void) pg_strip_crlf(rawline);

        if (strcmp(rawline, PG_MAJORVERSION) != 0)
        {
                pg_log_error("data directory is of wrong version");
                pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
                                                        ver_file, rawline, PG_MAJORVERSION);
                exit(1);
        }

        fclose(ver_fd);
}


/*
 * Try to read the existing pg_control file.
 *
 * This routine is also responsible for updating old pg_control versions
 * to the current format.  (Currently we don't do anything of the sort.)
 */
static bool
read_controlfile(void)
{
        int                     fd;
        int                     len;
        char       *buffer;
        pg_crc32c       crc;

        if ((fd = open(XLOG_CONTROL_FILE, O_RDONLY | PG_BINARY, 0)) < 0)
        {
                /*
                 * If pg_control is not there at all, or we can't read it, the odds
                 * are we've been handed a bad DataDir path, so give up. User can do
                 * "touch pg_control" to force us to proceed.
                 */
                pg_log_error("could not open file \"%s\" for reading: %m",
                                         XLOG_CONTROL_FILE);
                if (errno == ENOENT)
                        pg_log_error_hint("If you are sure the data directory path is correct, execute\n"
                                                          "  touch %s\n"
                                                          "and try again.",
                                                          XLOG_CONTROL_FILE);
                exit(1);
        }

        /* Use malloc to ensure we have a maxaligned buffer */
        buffer = (char *) pg_malloc(PG_CONTROL_FILE_SIZE);

        len = read(fd, buffer, PG_CONTROL_FILE_SIZE);
        if (len < 0)
                pg_fatal("could not read file \"%s\": %m", XLOG_CONTROL_FILE);
        close(fd);

        if (len >= sizeof(ControlFileData) &&
                ((ControlFileData *) buffer)->pg_control_version == PG_CONTROL_VERSION)
        {
                /* Check the CRC. */
                INIT_CRC32C(crc);
                COMP_CRC32C(crc,
                                        buffer,
                                        offsetof(ControlFileData, crc));
                FIN_CRC32C(crc);

                if (!EQ_CRC32C(crc, ((ControlFileData *) buffer)->crc))
                {
                        /* We will use the data but treat it as guessed. */
                        pg_log_warning("pg_control exists but has invalid CRC; proceed with caution");
                        guessed = true;
                }

                memcpy(&ControlFile, buffer, sizeof(ControlFile));

                /* return false if WAL segment size is not valid */
                if (!IsValidWalSegSize(ControlFile.xlog_seg_size))
                {
                        pg_log_warning(ngettext("pg_control specifies invalid WAL segment size (%d byte); proceed with caution",
                                                                        "pg_control specifies invalid WAL segment size (%d bytes); proceed with caution",
                                                                        ControlFile.xlog_seg_size),
                                                   ControlFile.xlog_seg_size);
                        return false;
                }

                return true;
        }

        /* Looks like it's a mess. */
        pg_log_warning("pg_control exists but is broken or wrong version; ignoring it");
        return false;
}


/*
 * Guess at pg_control values when we can't read the old ones.
 */
static void
GuessControlValues(void)
{
        uint64          sysidentifier;
        struct timeval tv;

        /*
         * Set up a completely default set of pg_control values.
         */
        guessed = true;
        memset(&ControlFile, 0, sizeof(ControlFile));

        ControlFile.pg_control_version = PG_CONTROL_VERSION;
        ControlFile.catalog_version_no = CATALOG_VERSION_NO;

        /*
         * Create a new unique installation identifier, since we can no longer use
         * any old XLOG records.  See notes in xlog.c about the algorithm.
         */
        gettimeofday(&tv, NULL);
        sysidentifier = ((uint64) tv.tv_sec) << 32;
        sysidentifier |= ((uint64) tv.tv_usec) << 12;
        sysidentifier |= getpid() & 0xFFF;

        ControlFile.system_identifier = sysidentifier;

        ControlFile.checkPointCopy.redo = SizeOfXLogLongPHD;
        ControlFile.checkPointCopy.ThisTimeLineID = 1;
        ControlFile.checkPointCopy.PrevTimeLineID = 1;
        ControlFile.checkPointCopy.fullPageWrites = false;
        ControlFile.checkPointCopy.nextXid =
                FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId);
        ControlFile.checkPointCopy.nextOid = FirstGenbkiObjectId;
        ControlFile.checkPointCopy.nextMulti = FirstMultiXactId;
        ControlFile.checkPointCopy.nextMultiOffset = 0;
        ControlFile.checkPointCopy.oldestXid = FirstNormalTransactionId;
        ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
        ControlFile.checkPointCopy.oldestMulti = FirstMultiXactId;
        ControlFile.checkPointCopy.oldestMultiDB = InvalidOid;
        ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);
        ControlFile.checkPointCopy.oldestActiveXid = InvalidTransactionId;

        ControlFile.state = DB_SHUTDOWNED;
        ControlFile.time = (pg_time_t) time(NULL);
        ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
        ControlFile.unloggedLSN = FirstNormalUnloggedLSN;

        /* minRecoveryPoint, backupStartPoint and backupEndPoint can be left zero */

        ControlFile.wal_level = WAL_LEVEL_MINIMAL;
        ControlFile.wal_log_hints = false;
        ControlFile.track_commit_timestamp = false;
        ControlFile.MaxConnections = 100;
        ControlFile.max_wal_senders = 10;
        ControlFile.max_worker_processes = 8;
        ControlFile.max_prepared_xacts = 0;
        ControlFile.max_locks_per_xact = 64;

        ControlFile.maxAlign = MAXIMUM_ALIGNOF;
        ControlFile.floatFormat = FLOATFORMAT_VALUE;
        ControlFile.blcksz = BLCKSZ;
        ControlFile.relseg_size = RELSEG_SIZE;
        ControlFile.xlog_blcksz = XLOG_BLCKSZ;
        ControlFile.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
        ControlFile.nameDataLen = NAMEDATALEN;
        ControlFile.indexMaxKeys = INDEX_MAX_KEYS;
        ControlFile.toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE;
        ControlFile.loblksize = LOBLKSIZE;
        ControlFile.float8ByVal = FLOAT8PASSBYVAL;

        /*
         * XXX eventually, should try to grovel through old XLOG to develop more
         * accurate values for TimeLineID, nextXID, etc.
         */
}


/*
 * Print the guessed pg_control values when we had to guess.
 *
 * NB: this display should be just those fields that will not be
 * reset by RewriteControlFile().
 */
static void
PrintControlValues(bool guessed)
{
        if (guessed)
                printf(_("Guessed pg_control values:\n\n"));
        else
                printf(_("Current pg_control values:\n\n"));

        printf(_("pg_control version number:            %u\n"),
                   ControlFile.pg_control_version);
        printf(_("Catalog version number:               %u\n"),
                   ControlFile.catalog_version_no);
        printf(_("Database system identifier:           %llu\n"),
                   (unsigned long long) ControlFile.system_identifier);
        printf(_("Latest checkpoint's TimeLineID:       %u\n"),
                   ControlFile.checkPointCopy.ThisTimeLineID);
        printf(_("Latest checkpoint's full_page_writes: %s\n"),
                   ControlFile.checkPointCopy.fullPageWrites ? _("on") : _("off"));
        printf(_("Latest checkpoint's NextXID:          %u:%u\n"),
                   EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid),
                   XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
        printf(_("Latest checkpoint's NextOID:          %u\n"),
                   ControlFile.checkPointCopy.nextOid);
        printf(_("Latest checkpoint's NextMultiXactId:  %u\n"),
                   ControlFile.checkPointCopy.nextMulti);
        printf(_("Latest checkpoint's NextMultiOffset:  %u\n"),
                   ControlFile.checkPointCopy.nextMultiOffset);
        printf(_("Latest checkpoint's oldestXID:        %u\n"),
                   ControlFile.checkPointCopy.oldestXid);
        printf(_("Latest checkpoint's oldestXID's DB:   %u\n"),
                   ControlFile.checkPointCopy.oldestXidDB);
        printf(_("Latest checkpoint's oldestActiveXID:  %u\n"),
                   ControlFile.checkPointCopy.oldestActiveXid);
        printf(_("Latest checkpoint's oldestMultiXid:   %u\n"),
                   ControlFile.checkPointCopy.oldestMulti);
        printf(_("Latest checkpoint's oldestMulti's DB: %u\n"),
                   ControlFile.checkPointCopy.oldestMultiDB);
        printf(_("Latest checkpoint's oldestCommitTsXid:%u\n"),
                   ControlFile.checkPointCopy.oldestCommitTsXid);
        printf(_("Latest checkpoint's newestCommitTsXid:%u\n"),
                   ControlFile.checkPointCopy.newestCommitTsXid);
        printf(_("Maximum data alignment:               %u\n"),
                   ControlFile.maxAlign);
        /* we don't print floatFormat since can't say much useful about it */
        printf(_("Database block size:                  %u\n"),
                   ControlFile.blcksz);
        printf(_("Blocks per segment of large relation: %u\n"),
                   ControlFile.relseg_size);
        printf(_("WAL block size:                       %u\n"),
                   ControlFile.xlog_blcksz);
        printf(_("Bytes per WAL segment:                %u\n"),
                   ControlFile.xlog_seg_size);
        printf(_("Maximum length of identifiers:        %u\n"),
                   ControlFile.nameDataLen);
        printf(_("Maximum columns in an index:          %u\n"),
                   ControlFile.indexMaxKeys);
        printf(_("Maximum size of a TOAST chunk:        %u\n"),
                   ControlFile.toast_max_chunk_size);
        printf(_("Size of a large-object chunk:         %u\n"),
                   ControlFile.loblksize);
        /* This is no longer configurable, but users may still expect to see it: */
        printf(_("Date/time type storage:               %s\n"),
                   _("64-bit integers"));
        printf(_("Float8 argument passing:              %s\n"),
                   (ControlFile.float8ByVal ? _("by value") : _("by reference")));
        printf(_("Data page checksum version:           %u\n"),
                   ControlFile.data_checksum_version);
}


/*
 * Print the values to be changed.
 */
static void
PrintNewControlValues(void)
{
        char            fname[MAXFNAMELEN];

        /* This will be always printed in order to keep format same. */
        printf(_("\n\nValues to be changed:\n\n"));

        XLogFileName(fname, ControlFile.checkPointCopy.ThisTimeLineID,
                                 newXlogSegNo, WalSegSz);
        printf(_("First log segment after reset:        %s\n"), fname);

        if (set_mxid != 0)
        {
                printf(_("NextMultiXactId:                      %u\n"),
                           ControlFile.checkPointCopy.nextMulti);
                printf(_("OldestMultiXid:                       %u\n"),
                           ControlFile.checkPointCopy.oldestMulti);
                printf(_("OldestMulti's DB:                     %u\n"),
                           ControlFile.checkPointCopy.oldestMultiDB);
        }

        if (set_mxoff != -1)
        {
                printf(_("NextMultiOffset:                      %u\n"),
                           ControlFile.checkPointCopy.nextMultiOffset);
        }

        if (set_oid != 0)
        {
                printf(_("NextOID:                              %u\n"),
                           ControlFile.checkPointCopy.nextOid);
        }

        if (set_xid != 0)
        {
                printf(_("NextXID:                              %u\n"),
                           XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
                printf(_("OldestXID:                            %u\n"),
                           ControlFile.checkPointCopy.oldestXid);
                printf(_("OldestXID's DB:                       %u\n"),
                           ControlFile.checkPointCopy.oldestXidDB);
        }

        if (set_xid_epoch != -1)
        {
                printf(_("NextXID epoch:                        %u\n"),
                           EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
        }

        if (set_oldest_commit_ts_xid != 0)
        {
                printf(_("oldestCommitTsXid:                    %u\n"),
                           ControlFile.checkPointCopy.oldestCommitTsXid);
        }
        if (set_newest_commit_ts_xid != 0)
        {
                printf(_("newestCommitTsXid:                    %u\n"),
                           ControlFile.checkPointCopy.newestCommitTsXid);
        }

        if (set_wal_segsize != 0)
        {
                printf(_("Bytes per WAL segment:                %u\n"),
                           ControlFile.xlog_seg_size);
        }
}


/*
 * Write out the new pg_control file.
 */
static void
RewriteControlFile(void)
{
        /*
         * Adjust fields as needed to force an empty XLOG starting at
         * newXlogSegNo.
         */
        XLogSegNoOffsetToRecPtr(newXlogSegNo, SizeOfXLogLongPHD, WalSegSz,
                                                        ControlFile.checkPointCopy.redo);
        ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);

        ControlFile.state = DB_SHUTDOWNED;
        ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
        ControlFile.minRecoveryPoint = 0;
        ControlFile.minRecoveryPointTLI = 0;
        ControlFile.backupStartPoint = 0;
        ControlFile.backupEndPoint = 0;
        ControlFile.backupEndRequired = false;

        /*
         * Force the defaults for max_* settings. The values don't really matter
         * as long as wal_level='minimal'; the postmaster will reset these fields
         * anyway at startup.
         */
        ControlFile.wal_level = WAL_LEVEL_MINIMAL;
        ControlFile.wal_log_hints = false;
        ControlFile.track_commit_timestamp = false;
        ControlFile.MaxConnections = 100;
        ControlFile.max_wal_senders = 10;
        ControlFile.max_worker_processes = 8;
        ControlFile.max_prepared_xacts = 0;
        ControlFile.max_locks_per_xact = 64;

        /* The control file gets flushed here. */
        update_controlfile(".", &ControlFile, true);
}


/*
 * Scan existing XLOG files and determine the highest existing WAL address
 *
 * On entry, ControlFile.checkPointCopy.redo and ControlFile.xlog_seg_size
 * are assumed valid (note that we allow the old xlog seg size to differ
 * from what we're using).  On exit, newXlogSegNo is set to suitable
 * value for the beginning of replacement WAL (in our seg size).
 */
static void
FindEndOfXLOG(void)
{
        DIR                *xldir;
        struct dirent *xlde;
        uint64          xlogbytepos;

        /*
         * Initialize the max() computation using the last checkpoint address from
         * old pg_control.  Note that for the moment we are working with segment
         * numbering according to the old xlog seg size.
         */
        XLByteToSeg(ControlFile.checkPointCopy.redo, newXlogSegNo,
                                ControlFile.xlog_seg_size);

        /*
         * Scan the pg_wal directory to find existing WAL segment files. We assume
         * any present have been used; in most scenarios this should be
         * conservative, because of xlog.c's attempts to pre-create files.
         */
        xldir = opendir(XLOGDIR);
        if (xldir == NULL)
                pg_fatal("could not open directory \"%s\": %m", XLOGDIR);

        while (errno = 0, (xlde = readdir(xldir)) != NULL)
        {
                if (IsXLogFileName(xlde->d_name) ||
                        IsPartialXLogFileName(xlde->d_name))
                {
                        TimeLineID      tli;
                        XLogSegNo       segno;

                        /* Use the segment size from the control file */
                        XLogFromFileName(xlde->d_name, &tli, &segno,
                                                         ControlFile.xlog_seg_size);

                        /*
                         * Note: we take the max of all files found, regardless of their
                         * timelines.  Another possibility would be to ignore files of
                         * timelines other than the target TLI, but this seems safer.
                         * Better too large a result than too small...
                         */
                        if (segno > newXlogSegNo)
                                newXlogSegNo = segno;
                }
        }

        if (errno)
                pg_fatal("could not read directory \"%s\": %m", XLOGDIR);

        if (closedir(xldir))
                pg_fatal("could not close directory \"%s\": %m", XLOGDIR);

        /*
         * Finally, convert to new xlog seg size, and advance by one to ensure we
         * are in virgin territory.
         */
        xlogbytepos = newXlogSegNo * ControlFile.xlog_seg_size;
        newXlogSegNo = (xlogbytepos + ControlFile.xlog_seg_size - 1) / WalSegSz;
        newXlogSegNo++;
}


/*
 * Remove existing XLOG files
 */
static void
KillExistingXLOG(void)
{
        DIR                *xldir;
        struct dirent *xlde;
        char            path[MAXPGPATH + sizeof(XLOGDIR)];

        xldir = opendir(XLOGDIR);
        if (xldir == NULL)
                pg_fatal("could not open directory \"%s\": %m", XLOGDIR);

        while (errno = 0, (xlde = readdir(xldir)) != NULL)
        {
                if (IsXLogFileName(xlde->d_name) ||
                        IsPartialXLogFileName(xlde->d_name))
                {
                        snprintf(path, sizeof(path), "%s/%s", XLOGDIR, xlde->d_name);
                        if (unlink(path) < 0)
                                pg_fatal("could not delete file \"%s\": %m", path);
                }
        }

        if (errno)
                pg_fatal("could not read directory \"%s\": %m", XLOGDIR);

        if (closedir(xldir))
                pg_fatal("could not close directory \"%s\": %m", XLOGDIR);
}


/*
 * Remove existing archive status files
 */
static void
KillExistingArchiveStatus(void)
{
#define ARCHSTATDIR XLOGDIR "/archive_status"

        DIR                *xldir;
        struct dirent *xlde;
        char            path[MAXPGPATH + sizeof(ARCHSTATDIR)];

        xldir = opendir(ARCHSTATDIR);
        if (xldir == NULL)
                pg_fatal("could not open directory \"%s\": %m", ARCHSTATDIR);

        while (errno = 0, (xlde = readdir(xldir)) != NULL)
        {
                if (strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_FNAME_LEN &&
                        (strcmp(xlde->d_name + XLOG_FNAME_LEN, ".ready") == 0 ||
                         strcmp(xlde->d_name + XLOG_FNAME_LEN, ".done") == 0 ||
                         strcmp(xlde->d_name + XLOG_FNAME_LEN, ".partial.ready") == 0 ||
                         strcmp(xlde->d_name + XLOG_FNAME_LEN, ".partial.done") == 0))
                {
                        snprintf(path, sizeof(path), "%s/%s", ARCHSTATDIR, xlde->d_name);
                        if (unlink(path) < 0)
                                pg_fatal("could not delete file \"%s\": %m", path);
                }
        }

        if (errno)
                pg_fatal("could not read directory \"%s\": %m", ARCHSTATDIR);

        if (closedir(xldir))
                pg_fatal("could not close directory \"%s\": %m", ARCHSTATDIR);
}

/*
 * Remove existing WAL summary files
 */
static void
KillExistingWALSummaries(void)
{
#define WALSUMMARYDIR XLOGDIR   "/summaries"
#define WALSUMMARY_NHEXCHARS    40

        DIR                *xldir;
        struct dirent *xlde;
        char            path[MAXPGPATH + sizeof(WALSUMMARYDIR)];

        xldir = opendir(WALSUMMARYDIR);
        if (xldir == NULL)
                pg_fatal("could not open directory \"%s\": %m", WALSUMMARYDIR);

        while (errno = 0, (xlde = readdir(xldir)) != NULL)
        {
                if (strspn(xlde->d_name, "0123456789ABCDEF") == WALSUMMARY_NHEXCHARS &&
                        strcmp(xlde->d_name + WALSUMMARY_NHEXCHARS, ".summary") == 0)
                {
                        snprintf(path, sizeof(path), "%s/%s", WALSUMMARYDIR, xlde->d_name);
                        if (unlink(path) < 0)
                                pg_fatal("could not delete file \"%s\": %m", path);
                }
        }

        if (errno)
                pg_fatal("could not read directory \"%s\": %m", WALSUMMARYDIR);

        if (closedir(xldir))
                pg_fatal("could not close directory \"%s\": %m", ARCHSTATDIR);
}

/*
 * Write an empty XLOG file, containing only the checkpoint record
 * already set up in ControlFile.
 */
static void
WriteEmptyXLOG(void)
{
        PGAlignedXLogBlock buffer;
        XLogPageHeader page;
        XLogLongPageHeader longpage;
        XLogRecord *record;
        pg_crc32c       crc;
        char            path[MAXPGPATH];
        int                     fd;
        int                     nbytes;
        char       *recptr;

        memset(buffer.data, 0, XLOG_BLCKSZ);

        /* Set up the XLOG page header */
        page = (XLogPageHeader) buffer.data;
        page->xlp_magic = XLOG_PAGE_MAGIC;
        page->xlp_info = XLP_LONG_HEADER;
        page->xlp_tli = ControlFile.checkPointCopy.ThisTimeLineID;
        page->xlp_pageaddr = ControlFile.checkPointCopy.redo - SizeOfXLogLongPHD;
        longpage = (XLogLongPageHeader) page;
        longpage->xlp_sysid = ControlFile.system_identifier;
        longpage->xlp_seg_size = WalSegSz;
        longpage->xlp_xlog_blcksz = XLOG_BLCKSZ;

        /* Insert the initial checkpoint record */
        recptr = (char *) page + SizeOfXLogLongPHD;
        record = (XLogRecord *) recptr;
        record->xl_prev = 0;
        record->xl_xid = InvalidTransactionId;
        record->xl_tot_len = SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(CheckPoint);
        record->xl_info = XLOG_CHECKPOINT_SHUTDOWN;
        record->xl_rmid = RM_XLOG_ID;

        recptr += SizeOfXLogRecord;
        *(recptr++) = (char) XLR_BLOCK_ID_DATA_SHORT;
        *(recptr++) = sizeof(CheckPoint);
        memcpy(recptr, &ControlFile.checkPointCopy,
                   sizeof(CheckPoint));

        INIT_CRC32C(crc);
        COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord);
        COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
        FIN_CRC32C(crc);
        record->xl_crc = crc;

        /* Write the first page */
        XLogFilePath(path, ControlFile.checkPointCopy.ThisTimeLineID,
                                 newXlogSegNo, WalSegSz);

        unlink(path);

        fd = open(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                          pg_file_create_mode);
        if (fd < 0)
                pg_fatal("could not open file \"%s\": %m", path);

        errno = 0;
        if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
        {
                /* if write didn't set errno, assume problem is no disk space */
                if (errno == 0)
                        errno = ENOSPC;
                pg_fatal("could not write file \"%s\": %m", path);
        }

        /* Fill the rest of the file with zeroes */
        memset(buffer.data, 0, XLOG_BLCKSZ);
        for (nbytes = XLOG_BLCKSZ; nbytes < WalSegSz; nbytes += XLOG_BLCKSZ)
        {
                errno = 0;
                if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
                {
                        if (errno == 0)
                                errno = ENOSPC;
                        pg_fatal("could not write file \"%s\": %m", path);
                }
        }

        if (fsync(fd) != 0)
                pg_fatal("fsync error: %m");

        close(fd);
}


static void
usage(void)
{
        printf(_("%s resets the PostgreSQL write-ahead log.\n\n"), progname);
        printf(_("Usage:\n"));
        printf(_("  %s [OPTION]... DATADIR\n"), progname);

        printf(_("\nOptions:\n"));
        printf(_(" [-D, --pgdata=]DATADIR  data directory\n"));
        printf(_("  -f, --force            force update to be done even after unclean shutdown or\n"
                         "                         if pg_control values had to be guessed\n"));
        printf(_("  -n, --dry-run          no update, just show what would be done\n"));
        printf(_("  -V, --version          output version information, then exit\n"));
        printf(_("  -?, --help             show this help, then exit\n"));

        printf(_("\nOptions to override control file values:\n"));
        printf(_("  -c, --commit-timestamp-ids=XID,XID\n"
                         "                                   set oldest and newest transactions bearing\n"
                         "                                   commit timestamp (zero means no change)\n"));
        printf(_("  -e, --epoch=XIDEPOCH             set next transaction ID epoch\n"));
        printf(_("  -l, --next-wal-file=WALFILE      set minimum starting location for new WAL\n"));
        printf(_("  -m, --multixact-ids=MXID,MXID    set next and oldest multitransaction ID\n"));
        printf(_("  -o, --next-oid=OID               set next OID\n"));
        printf(_("  -O, --multixact-offset=OFFSET    set next multitransaction offset\n"));
        printf(_("  -u, --oldest-transaction-id=XID  set oldest transaction ID\n"));
        printf(_("  -x, --next-transaction-id=XID    set next transaction ID\n"));
        printf(_("      --wal-segsize=SIZE           size of WAL segments, in megabytes\n"));

        printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
        printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
}