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pg_control.h

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00001 /*-------------------------------------------------------------------------
00002  *
00003  * pg_control.h
00004  *    The system control file "pg_control" is not a heap relation.
00005  *    However, we define it here so that the format is documented.
00006  *
00007  *
00008  * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
00009  * Portions Copyright (c) 1994, Regents of the University of California
00010  *
00011  * src/include/catalog/pg_control.h
00012  *
00013  *-------------------------------------------------------------------------
00014  */
00015 #ifndef PG_CONTROL_H
00016 #define PG_CONTROL_H
00017 
00018 #include "access/xlogdefs.h"
00019 #include "pgtime.h"             /* for pg_time_t */
00020 #include "utils/pg_crc.h"
00021 
00022 
00023 /* Version identifier for this pg_control format */
00024 #define PG_CONTROL_VERSION  937
00025 
00026 /*
00027  * Body of CheckPoint XLOG records.  This is declared here because we keep
00028  * a copy of the latest one in pg_control for possible disaster recovery.
00029  * Changing this struct requires a PG_CONTROL_VERSION bump.
00030  */
00031 typedef struct CheckPoint
00032 {
00033     XLogRecPtr  redo;           /* next RecPtr available when we began to
00034                                  * create CheckPoint (i.e. REDO start point) */
00035     TimeLineID  ThisTimeLineID; /* current TLI */
00036     TimeLineID  PrevTimeLineID; /* previous TLI, if this record begins a new
00037                                  * timeline (equals ThisTimeLineID otherwise) */
00038     bool        fullPageWrites; /* current full_page_writes */
00039     uint32      nextXidEpoch;   /* higher-order bits of nextXid */
00040     TransactionId nextXid;      /* next free XID */
00041     Oid         nextOid;        /* next free OID */
00042     MultiXactId nextMulti;      /* next free MultiXactId */
00043     MultiXactOffset nextMultiOffset;    /* next free MultiXact offset */
00044     TransactionId oldestXid;    /* cluster-wide minimum datfrozenxid */
00045     Oid         oldestXidDB;    /* database with minimum datfrozenxid */
00046     MultiXactId oldestMulti;    /* cluster-wide minimum datminmxid */
00047     Oid         oldestMultiDB;  /* database with minimum datminmxid */
00048     pg_time_t   time;           /* time stamp of checkpoint */
00049 
00050     /*
00051      * Oldest XID still running. This is only needed to initialize hot standby
00052      * mode from an online checkpoint, so we only bother calculating this for
00053      * online checkpoints and only when wal_level is hot_standby. Otherwise
00054      * it's set to InvalidTransactionId.
00055      */
00056     TransactionId oldestActiveXid;
00057 } CheckPoint;
00058 
00059 /* XLOG info values for XLOG rmgr */
00060 #define XLOG_CHECKPOINT_SHUTDOWN        0x00
00061 #define XLOG_CHECKPOINT_ONLINE          0x10
00062 #define XLOG_NOOP                       0x20
00063 #define XLOG_NEXTOID                    0x30
00064 #define XLOG_SWITCH                     0x40
00065 #define XLOG_BACKUP_END                 0x50
00066 #define XLOG_PARAMETER_CHANGE           0x60
00067 #define XLOG_RESTORE_POINT              0x70
00068 #define XLOG_FPW_CHANGE                 0x80
00069 #define XLOG_END_OF_RECOVERY            0x90
00070 #define XLOG_HINT                       0xA0
00071 
00072 
00073 /*
00074  * System status indicator.  Note this is stored in pg_control; if you change
00075  * it, you must bump PG_CONTROL_VERSION
00076  */
00077 typedef enum DBState
00078 {
00079     DB_STARTUP = 0,
00080     DB_SHUTDOWNED,
00081     DB_SHUTDOWNED_IN_RECOVERY,
00082     DB_SHUTDOWNING,
00083     DB_IN_CRASH_RECOVERY,
00084     DB_IN_ARCHIVE_RECOVERY,
00085     DB_IN_PRODUCTION
00086 } DBState;
00087 
00088 /*
00089  * Contents of pg_control.
00090  *
00091  * NOTE: try to keep this under 512 bytes so that it will fit on one physical
00092  * sector of typical disk drives.  This reduces the odds of corruption due to
00093  * power failure midway through a write.
00094  */
00095 
00096 typedef struct ControlFileData
00097 {
00098     /*
00099      * Unique system identifier --- to ensure we match up xlog files with the
00100      * installation that produced them.
00101      */
00102     uint64      system_identifier;
00103 
00104     /*
00105      * Version identifier information.  Keep these fields at the same offset,
00106      * especially pg_control_version; they won't be real useful if they move
00107      * around.  (For historical reasons they must be 8 bytes into the file
00108      * rather than immediately at the front.)
00109      *
00110      * pg_control_version identifies the format of pg_control itself.
00111      * catalog_version_no identifies the format of the system catalogs.
00112      *
00113      * There are additional version identifiers in individual files; for
00114      * example, WAL logs contain per-page magic numbers that can serve as
00115      * version cues for the WAL log.
00116      */
00117     uint32      pg_control_version;     /* PG_CONTROL_VERSION */
00118     uint32      catalog_version_no;     /* see catversion.h */
00119 
00120     /*
00121      * System status data
00122      */
00123     DBState     state;          /* see enum above */
00124     pg_time_t   time;           /* time stamp of last pg_control update */
00125     XLogRecPtr  checkPoint;     /* last check point record ptr */
00126     XLogRecPtr  prevCheckPoint; /* previous check point record ptr */
00127 
00128     CheckPoint  checkPointCopy; /* copy of last check point record */
00129 
00130     XLogRecPtr  unloggedLSN;    /* current fake LSN value, for unlogged rels */
00131 
00132     /*
00133      * These two values determine the minimum point we must recover up to
00134      * before starting up:
00135      *
00136      * minRecoveryPoint is updated to the latest replayed LSN whenever we
00137      * flush a data change during archive recovery. That guards against
00138      * starting archive recovery, aborting it, and restarting with an earlier
00139      * stop location. If we've already flushed data changes from WAL record X
00140      * to disk, we mustn't start up until we reach X again. Zero when not
00141      * doing archive recovery.
00142      *
00143      * backupStartPoint is the redo pointer of the backup start checkpoint, if
00144      * we are recovering from an online backup and haven't reached the end of
00145      * backup yet. It is reset to zero when the end of backup is reached, and
00146      * we mustn't start up before that. A boolean would suffice otherwise, but
00147      * we use the redo pointer as a cross-check when we see an end-of-backup
00148      * record, to make sure the end-of-backup record corresponds the base
00149      * backup we're recovering from.
00150      *
00151      * backupEndPoint is the backup end location, if we are recovering from an
00152      * online backup which was taken from the standby and haven't reached the
00153      * end of backup yet. It is initialized to the minimum recovery point in
00154      * pg_control which was backed up last. It is reset to zero when the end
00155      * of backup is reached, and we mustn't start up before that.
00156      *
00157      * If backupEndRequired is true, we know for sure that we're restoring
00158      * from a backup, and must see a backup-end record before we can safely
00159      * start up. If it's false, but backupStartPoint is set, a backup_label
00160      * file was found at startup but it may have been a leftover from a stray
00161      * pg_start_backup() call, not accompanied by pg_stop_backup().
00162      */
00163     XLogRecPtr  minRecoveryPoint;
00164     TimeLineID  minRecoveryPointTLI;
00165     XLogRecPtr  backupStartPoint;
00166     XLogRecPtr  backupEndPoint;
00167     bool        backupEndRequired;
00168 
00169     /*
00170      * Parameter settings that determine if the WAL can be used for archival
00171      * or hot standby.
00172      */
00173     int         wal_level;
00174     int         MaxConnections;
00175     int         max_prepared_xacts;
00176     int         max_locks_per_xact;
00177 
00178     /*
00179      * This data is used to check for hardware-architecture compatibility of
00180      * the database and the backend executable.  We need not check endianness
00181      * explicitly, since the pg_control version will surely look wrong to a
00182      * machine of different endianness, but we do need to worry about MAXALIGN
00183      * and floating-point format.  (Note: storage layout nominally also
00184      * depends on SHORTALIGN and INTALIGN, but in practice these are the same
00185      * on all architectures of interest.)
00186      *
00187      * Testing just one double value is not a very bulletproof test for
00188      * floating-point compatibility, but it will catch most cases.
00189      */
00190     uint32      maxAlign;       /* alignment requirement for tuples */
00191     double      floatFormat;    /* constant 1234567.0 */
00192 #define FLOATFORMAT_VALUE   1234567.0
00193 
00194     /*
00195      * This data is used to make sure that configuration of this database is
00196      * compatible with the backend executable.
00197      */
00198     uint32      blcksz;         /* data block size for this DB */
00199     uint32      relseg_size;    /* blocks per segment of large relation */
00200 
00201     uint32      xlog_blcksz;    /* block size within WAL files */
00202     uint32      xlog_seg_size;  /* size of each WAL segment */
00203 
00204     uint32      nameDataLen;    /* catalog name field width */
00205     uint32      indexMaxKeys;   /* max number of columns in an index */
00206 
00207     uint32      toast_max_chunk_size;   /* chunk size in TOAST tables */
00208 
00209     /* flag indicating internal format of timestamp, interval, time */
00210     bool        enableIntTimes; /* int64 storage enabled? */
00211 
00212     /* flags indicating pass-by-value status of various types */
00213     bool        float4ByVal;    /* float4 pass-by-value? */
00214     bool        float8ByVal;    /* float8, int8, etc pass-by-value? */
00215 
00216     /* Are data pages protected by checksums? Zero if no checksum version */
00217     uint32      data_checksum_version;
00218 
00219     /* CRC of all above ... MUST BE LAST! */
00220     pg_crc32    crc;
00221 } ControlFileData;
00222 
00223 /*
00224  * Physical size of the pg_control file.  Note that this is considerably
00225  * bigger than the actually used size (ie, sizeof(ControlFileData)).
00226  * The idea is to keep the physical size constant independent of format
00227  * changes, so that ReadControlFile will deliver a suitable wrong-version
00228  * message instead of a read error if it's looking at an incompatible file.
00229  */
00230 #define PG_CONTROL_SIZE     8192
00231 
00232 #endif   /* PG_CONTROL_H */