src/include/catalog/pg_control.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pg_control.h
   4  *        The system control file "pg_control" is not a heap relation.
   5  *        However, we define it here so that the format is documented.
   6  *
   7  *
   8  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * $PostgreSQL$
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #ifndef PG_CONTROL_H
  16 #define PG_CONTROL_H
  17
  18 #include "access/xlogdefs.h"
  19 #include "pgtime.h"                             /* for pg_time_t */
  20 #include "utils/pg_crc.h"
  21
  22
  23 /* Version identifier for this pg_control format */
  24 #define PG_CONTROL_VERSION      843
  25
  26 /*
  27  * Body of CheckPoint XLOG records.  This is declared here because we keep
  28  * a copy of the latest one in pg_control for possible disaster recovery.
  29  */
  30 typedef struct CheckPoint
  31 {
  32         XLogRecPtr      redo;                   /* next RecPtr available when we began to
  33                                                                  * create CheckPoint (i.e. REDO start point) */
  34         TimeLineID      ThisTimeLineID; /* current TLI */
  35         uint32          nextXidEpoch;   /* higher-order bits of nextXid */
  36         TransactionId nextXid;          /* next free XID */
  37         Oid                     nextOid;                /* next free OID */
  38         MultiXactId nextMulti;          /* next free MultiXactId */
  39         MultiXactOffset nextMultiOffset;        /* next free MultiXact offset */
  40         pg_time_t       time;                   /* time stamp of checkpoint */
  41 } CheckPoint;
  42
  43 /* XLOG info values for XLOG rmgr */
  44 #define XLOG_CHECKPOINT_SHUTDOWN                0x00
  45 #define XLOG_CHECKPOINT_ONLINE                  0x10
  46 #define XLOG_NOOP                                               0x20
  47 #define XLOG_NEXTOID                                    0x30
  48 #define XLOG_SWITCH                                             0x40
  49
  50
  51 /* System status indicator */
  52 typedef enum DBState
  53 {
  54         DB_STARTUP = 0,
  55         DB_SHUTDOWNED,
  56         DB_SHUTDOWNING,
  57         DB_IN_CRASH_RECOVERY,
  58         DB_IN_ARCHIVE_RECOVERY,
  59         DB_IN_PRODUCTION
  60 } DBState;
  61
  62 /*
  63  * Contents of pg_control.
  64  *
  65  * NOTE: try to keep this under 512 bytes so that it will fit on one physical
  66  * sector of typical disk drives.  This reduces the odds of corruption due to
  67  * power failure midway through a write.
  68  */
  69
  70 typedef struct ControlFileData
  71 {
  72         /*
  73          * Unique system identifier --- to ensure we match up xlog files with the
  74          * installation that produced them.
  75          */
  76         uint64          system_identifier;
  77
  78         /*
  79          * Version identifier information.      Keep these fields at the same offset,
  80          * especially pg_control_version; they won't be real useful if they move
  81          * around.      (For historical reasons they must be 8 bytes into the file
  82          * rather than immediately at the front.)
  83          *
  84          * pg_control_version identifies the format of pg_control itself.
  85          * catalog_version_no identifies the format of the system catalogs.
  86          *
  87          * There are additional version identifiers in individual files; for
  88          * example, WAL logs contain per-page magic numbers that can serve as
  89          * version cues for the WAL log.
  90          */
  91         uint32          pg_control_version;             /* PG_CONTROL_VERSION */
  92         uint32          catalog_version_no;             /* see catversion.h */
  93
  94         /*
  95          * System status data
  96          */
  97         DBState         state;                  /* see enum above */
  98         pg_time_t       time;                   /* time stamp of last pg_control update */
  99         XLogRecPtr      checkPoint;             /* last check point record ptr */
 100         XLogRecPtr      prevCheckPoint; /* previous check point record ptr */
 101
 102         CheckPoint      checkPointCopy; /* copy of last check point record */
 103
 104         XLogRecPtr      minRecoveryPoint;               /* must replay xlog to here */
 105
 106         /*
 107          * This data is used to check for hardware-architecture compatibility of
 108          * the database and the backend executable.  We need not check endianness
 109          * explicitly, since the pg_control version will surely look wrong to a
 110          * machine of different endianness, but we do need to worry about MAXALIGN
 111          * and floating-point format.  (Note: storage layout nominally also
 112          * depends on SHORTALIGN and INTALIGN, but in practice these are the same
 113          * on all architectures of interest.)
 114          *
 115          * Testing just one double value is not a very bulletproof test for
 116          * floating-point compatibility, but it will catch most cases.
 117          */
 118         uint32          maxAlign;               /* alignment requirement for tuples */
 119         double          floatFormat;    /* constant 1234567.0 */
 120 #define FLOATFORMAT_VALUE       1234567.0
 121
 122         /*
 123          * This data is used to make sure that configuration of this database is
 124          * compatible with the backend executable.
 125          */
 126         uint32          blcksz;                 /* data block size for this DB */
 127         uint32          relseg_size;    /* blocks per segment of large relation */
 128
 129         uint32          xlog_blcksz;    /* block size within WAL files */
 130         uint32          xlog_seg_size;  /* size of each WAL segment */
 131
 132         uint32          nameDataLen;    /* catalog name field width */
 133         uint32          indexMaxKeys;   /* max number of columns in an index */
 134
 135         uint32          toast_max_chunk_size;   /* chunk size in TOAST tables */
 136
 137         /* flag indicating internal format of timestamp, interval, time */
 138         bool            enableIntTimes; /* int64 storage enabled? */
 139
 140         /* flags indicating pass-by-value status of various types */
 141         bool            float4ByVal;    /* float4 pass-by-value? */
 142         bool            float8ByVal;    /* float8, int8, etc pass-by-value? */
 143
 144         /* CRC of all above ... MUST BE LAST! */
 145         pg_crc32        crc;
 146 } ControlFileData;
 147
 148 /*
 149  * Physical size of the pg_control file.  Note that this is considerably
 150  * bigger than the actually used size (ie, sizeof(ControlFileData)).
 151  * The idea is to keep the physical size constant independent of format
 152  * changes, so that ReadControlFile will deliver a suitable wrong-version
 153  * message instead of a read error if it's looking at an incompatible file.
 154  */
 155 #define PG_CONTROL_SIZE         8192
 156
 157 #endif   /* PG_CONTROL_H */