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/*
* xlogdefs.h
*
* Postgres write-ahead log manager record pointer and
* timeline number definitions
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/xlogdefs.h
*/
#ifndef XLOG_DEFS_H
#define XLOG_DEFS_H
#include <fcntl.h> /* need open() flags */
/*
* Pointer to a location in the XLOG. These pointers are 64 bits wide,
* because we don't want them ever to overflow.
*/
typedef uint64 XLogRecPtr;
/*
* Zero is used indicate an invalid pointer. Bootstrap skips the first possible
* WAL segment, initializing the first WAL page at WAL segment size, so no XLOG
* record can begin at zero.
*/
#define InvalidXLogRecPtr 0
#define XLogRecPtrIsInvalid(r) ((r) == InvalidXLogRecPtr)
/*
* First LSN to use for "fake" LSNs.
*
* Values smaller than this can be used for special per-AM purposes.
*/
#define FirstNormalUnloggedLSN ((XLogRecPtr) 1000)
/*
* Handy macro for printing XLogRecPtr in conventional format, e.g.,
*
* printf("%X/%X", LSN_FORMAT_ARGS(lsn));
*/
#define LSN_FORMAT_ARGS(lsn) (AssertVariableIsOfTypeMacro((lsn), XLogRecPtr), (uint32) ((lsn) >> 32)), ((uint32) (lsn))
/*
* XLogSegNo - physical log file sequence number.
*/
typedef uint64 XLogSegNo;
/*
* TimeLineID (TLI) - identifies different database histories to prevent
* confusion after restoring a prior state of a database installation.
* TLI does not change in a normal stop/restart of the database (including
* crash-and-recover cases); but we must assign a new TLI after doing
* a recovery to a prior state, a/k/a point-in-time recovery. This makes
* the new WAL logfile sequence we generate distinguishable from the
* sequence that was generated in the previous incarnation.
*/
typedef uint32 TimeLineID;
/*
* Replication origin id - this is located in this file to avoid having to
* include origin.h in a bunch of xlog related places.
*/
typedef uint16 RepOriginId;
/*
* This chunk of hackery attempts to determine which file sync methods
* are available on the current platform, and to choose an appropriate
* default method.
*
* Note that we define our own O_DSYNC on Windows, but not O_SYNC.
*/
#if defined(PLATFORM_DEFAULT_SYNC_METHOD)
#define DEFAULT_SYNC_METHOD PLATFORM_DEFAULT_SYNC_METHOD
#elif defined(O_DSYNC) && (!defined(O_SYNC) || O_DSYNC != O_SYNC)
#define DEFAULT_SYNC_METHOD SYNC_METHOD_OPEN_DSYNC
#else
#define DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC
#endif
#endif /* XLOG_DEFS_H */
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