text: /*-------------------------------------------------------------------------
   *
   * pg_control.h
   *	  The system control file "pg_control" is not a heap relation.
   *	  However, we define it here so that the format is documented.
   *
   *
   * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.33 2006/10/04 00:30:07 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
  #ifndef PG_CONTROL_H
  #define PG_CONTROL_H
  
  #include <time.h>
  
  #include "access/xlogdefs.h"
  #include "utils/pg_crc.h"
  #include "port/pg_crc32c.h"
  
  
  /* Version identifier for this pg_control format */
  #define PG_CONTROL_VERSION	822
  
  /*
   * Body of CheckPoint XLOG records.  This is declared here because we keep
   * a copy of the latest one in pg_control for possible disaster recovery.
   */
  typedef struct CheckPoint
  {
  	XLogRecPtr	redo;			/* next RecPtr available when we began to
  								 * create CheckPoint (i.e. REDO start point) */
  	XLogRecPtr	undo;			/* first record of oldest in-progress
  								 * transaction when we started (i.e. UNDO end
  								 * point) */
  	TimeLineID	ThisTimeLineID; /* current TLI */
  	uint32		nextXidEpoch;	/* higher-order bits of nextXid */
  	TransactionId nextXid;		/* next free XID */
  	Oid			nextOid;		/* next free OID */
  	MultiXactId nextMulti;		/* next free MultiXactId */
  	MultiXactOffset nextMultiOffset;	/* next free MultiXact offset */
  	time_t		time;			/* time stamp of checkpoint */
  
  	/* IN XLOG RECORD, MORE DATA FOLLOWS AT END OF STRUCT FOR DTM CHECKPOINT */
  
  } CheckPoint;
  
  /* XLOG info values for XLOG rmgr */
  #define XLOG_CHECKPOINT_SHUTDOWN		0x00
  #define XLOG_CHECKPOINT_ONLINE			0x10
  #define XLOG_NEXTOID					0x30
  #define XLOG_SWITCH						0x40
  
  
  /* System status indicator */
  typedef enum DBState
  {
  	DB_STARTUP = 0,
  	DB_SHUTDOWNED,
  	DB_SHUTDOWNING,
      DB_IN_CRASH_RECOVERY,
      DB_IN_ARCHIVE_RECOVERY,
  	DB_IN_PRODUCTION
  } DBState;
  
  #define LOCALE_NAME_BUFLEN	128
  
  /*
   * Contents of pg_control.
   *
   * NOTE: try to keep this under 512 bytes so that it will fit on one physical
   * sector of typical disk drives.  This reduces the odds of corruption due to
   * power failure midway through a write.  Currently it fits comfortably,
   * but we could probably reduce LOCALE_NAME_BUFLEN if things get tight.
   */
  
  typedef struct ControlFileData
  {
  	/*
  	 * Unique system identifier --- to ensure we match up xlog files with the
  	 * installation that produced them.
  	 */
  	uint64		system_identifier;
  
  	/*
  	 * Version identifier information.	Keep these fields at the same offset,
  	 * especially pg_control_version; they won't be real useful if they move
  	 * around.	(For historical reasons they must be 8 bytes into the file
  	 * rather than immediately at the front.)
  	 *
  	 * pg_control_version identifies the format of pg_control itself.
  	 * catalog_version_no identifies the format of the system catalogs.
  	 *
  	 * There are additional version identifiers in individual files; for
  	 * example, WAL logs contain per-page magic numbers that can serve as
  	 * version cues for the WAL log.
  	 */
  	uint32		pg_control_version;		/* PG_CONTROL_VERSION */
  	uint32		catalog_version_no;		/* see catversion.h */
  
  	/*
  	 * System status data
  	 */
  	DBState		state;			/* see enum above */
  	time_t		time;			/* time stamp of last pg_control update */
  	uint32		logId;			/* current log file id */
  	uint32		logSeg;			/* current log file segment, + 1 */
  	XLogRecPtr	checkPoint;		/* last check point record ptr */
  	XLogRecPtr	prevCheckPoint; /* previous check point record ptr */
  
  	CheckPoint	checkPointCopy; /* copy of last check point record */
  
  	XLogRecPtr	minRecoveryPoint;		/* must replay xlog to here */
  
  	/*
  	 * This data is used to check for hardware-architecture compatibility of
  	 * the database and the backend executable.  We need not check endianness
  	 * explicitly, since the pg_control version will surely look wrong to a
  	 * machine of different endianness, but we do need to worry about MAXALIGN
  	 * and floating-point format.  (Note: storage layout nominally also
  	 * depends on SHORTALIGN and INTALIGN, but in practice these are the same
  	 * on all architectures of interest.)
  	 *
  	 * Testing just one double value is not a very bulletproof test for
  	 * floating-point compatibility, but it will catch most cases.
  	 */
  	uint32		maxAlign;		/* alignment requirement for tuples */
  	double		floatFormat;	/* constant 1234567.0 */
  #define FLOATFORMAT_VALUE	1234567.0
  
  	/*
  	 * This data is used to make sure that configuration of this database is
  	 * compatible with the backend executable.
  	 */
  	uint32		blcksz;			/* data block size for this DB */
  	uint32		relseg_size;	/* blocks per segment of large relation */
  
  	uint32		xlog_blcksz;	/* block size within WAL files */
  	uint32		xlog_seg_size;	/* size of each WAL segment */
  
  	uint32		nameDataLen;	/* catalog name field width */
  	uint32		indexMaxKeys;	/* max number of columns in an index */
  
  	/* flag indicating internal format of timestamp, interval, time */
  	uint32		enableIntTimes; /* int64 storage enabled? */
  
  	/* active locales */
  	uint32		localeBuflen;
  	char		lc_collate[LOCALE_NAME_BUFLEN];
  	char		lc_ctype[LOCALE_NAME_BUFLEN];
  
  	/* CRC of all above ... MUST BE LAST! */
  	pg_crc32	crc;
  } ControlFileData;
  
  /*
   * Physical size of the pg_control file.  Note that this is considerably
   * bigger than the actually used size (ie, sizeof(ControlFileData)).
   * The idea is to keep the physical size constant independent of format
   * changes, so that ReadControlFile will deliver a suitable wrong-version
   * message instead of a read error if it's looking at an incompatible file.
   */
  #define PG_CONTROL_SIZE		8192
  
  #endif   /* PG_CONTROL_H */
  