diff options
Diffstat (limited to 'src/include/access/xlogdefs.h')
| -rw-r--r-- | src/include/access/xlogdefs.h | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/src/include/access/xlogdefs.h b/src/include/access/xlogdefs.h new file mode 100644 index 0000000..e1f5812 --- /dev/null +++ b/src/include/access/xlogdefs.h @@ -0,0 +1,109 @@ +/* + * xlogdefs.h + * + * Postgres write-ahead log manager record pointer and + * timeline number definitions + * + * Portions Copyright (c) 1996-2020, 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) + +/* + * 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; + +/* + * Because O_DIRECT bypasses the kernel buffers, and because we never + * read those buffers except during crash recovery or if wal_level != minimal, + * it is a win to use it in all cases where we sync on each write(). We could + * allow O_DIRECT with fsync(), but it is unclear if fsync() could process + * writes not buffered in the kernel. Also, O_DIRECT is never enough to force + * data to the drives, it merely tries to bypass the kernel cache, so we still + * need O_SYNC/O_DSYNC. + */ +#ifdef O_DIRECT +#define PG_O_DIRECT O_DIRECT +#else +#define PG_O_DIRECT 0 +#endif + +/* + * This chunk of hackery attempts to determine which file sync methods + * are available on the current platform, and to choose an appropriate + * default method. We assume that fsync() is always available, and that + * configure determined whether fdatasync() is. + */ +#if defined(O_SYNC) +#define OPEN_SYNC_FLAG O_SYNC +#elif defined(O_FSYNC) +#define OPEN_SYNC_FLAG O_FSYNC +#endif + +#if defined(O_DSYNC) +#if defined(OPEN_SYNC_FLAG) +/* O_DSYNC is distinct? */ +#if O_DSYNC != OPEN_SYNC_FLAG +#define OPEN_DATASYNC_FLAG O_DSYNC +#endif +#else /* !defined(OPEN_SYNC_FLAG) */ +/* Win32 only has O_DSYNC */ +#define OPEN_DATASYNC_FLAG O_DSYNC +#endif +#endif + +#if defined(PLATFORM_DEFAULT_SYNC_METHOD) +#define DEFAULT_SYNC_METHOD PLATFORM_DEFAULT_SYNC_METHOD +#elif defined(OPEN_DATASYNC_FLAG) +#define DEFAULT_SYNC_METHOD SYNC_METHOD_OPEN_DSYNC +#elif defined(HAVE_FDATASYNC) +#define DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC +#else +#define DEFAULT_SYNC_METHOD SYNC_METHOD_FSYNC +#endif + +#endif /* XLOG_DEFS_H */ |