xlogutils.h

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/*
 * xlogutils.h
 *
 * Utilities for replaying WAL records.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/xlogutils.h
 */
#ifndef XLOG_UTILS_H
#define XLOG_UTILS_H
 
#include "access/xlogreader.h"
#include "storage/bufmgr.h"
 
/* GUC variable */
extern PGDLLIMPORT bool ignore_invalid_pages;
 
/*
 * Prior to 8.4, all activity during recovery was carried out by the startup
 * process. This local variable continues to be used in many parts of the
 * code to indicate actions taken by RecoveryManagers. Other processes that
 * potentially perform work during recovery should check RecoveryInProgress().
 * See XLogCtl notes in xlog.c.
 */
extern PGDLLIMPORT bool InRecovery;
 
/*
 * Like InRecovery, standbyState is only valid in the startup process.
 * In all other processes it will have the value STANDBY_DISABLED (so
 * InHotStandby will read as false).
 *
 * In DISABLED state, we're performing crash recovery or hot standby was
 * disabled in postgresql.conf.
 *
 * In INITIALIZED state, we've run InitRecoveryTransactionEnvironment, but
 * we haven't yet processed a RUNNING_XACTS or shutdown-checkpoint WAL record
 * to initialize our primary-transaction tracking system.
 *
 * When the transaction tracking is initialized, we enter the SNAPSHOT_PENDING
 * state. The tracked information might still be incomplete, so we can't allow
 * connections yet, but redo functions must update the in-memory state when
 * appropriate.
 *
 * In SNAPSHOT_READY mode, we have full knowledge of transactions that are
 * (or were) running on the primary at the current WAL location. Snapshots
 * can be taken, and read-only queries can be run.
 */
typedef enum
{
    STANDBY_DISABLED,
    STANDBY_INITIALIZED,
    STANDBY_SNAPSHOT_PENDING,
    STANDBY_SNAPSHOT_READY,
} HotStandbyState;
 
extern PGDLLIMPORT HotStandbyState standbyState;
 
#define InHotStandby (standbyState >= STANDBY_SNAPSHOT_PENDING)
 
 
extern bool XLogHaveInvalidPages(void);
extern void XLogCheckInvalidPages(void);
 
extern void XLogDropRelation(RelFileLocator rlocator, ForkNumber forknum);
extern void XLogDropDatabase(Oid dbid);
extern void XLogTruncateRelation(RelFileLocator rlocator, ForkNumber forkNum,
                                 BlockNumber nblocks);
 
/* Result codes for XLogReadBufferForRedo[Extended] */
typedef enum
{
    BLK_NEEDS_REDO,             /* changes from WAL record need to be applied */
    BLK_DONE,                   /* block is already up-to-date */
    BLK_RESTORED,               /* block was restored from a full-page image */
    BLK_NOTFOUND,               /* block was not found (and hence does not
                                 * need to be replayed) */
} XLogRedoAction;
 
/* Private data of the read_local_xlog_page_no_wait callback. */
typedef struct ReadLocalXLogPageNoWaitPrivate
{
    bool        end_of_wal;     /* true, when end of WAL is reached */
} ReadLocalXLogPageNoWaitPrivate;
 
extern XLogRedoAction XLogReadBufferForRedo(XLogReaderState *record,
                                            uint8 block_id, Buffer *buf);
extern Buffer XLogInitBufferForRedo(XLogReaderState *record, uint8 block_id);
extern XLogRedoAction XLogReadBufferForRedoExtended(XLogReaderState *record,
                                                    uint8 block_id,
                                                    ReadBufferMode mode, bool get_cleanup_lock,
                                                    Buffer *buf);
 
extern Buffer XLogReadBufferExtended(RelFileLocator rlocator, ForkNumber forknum,
                                     BlockNumber blkno, ReadBufferMode mode,
                                     Buffer recent_buffer);
 
extern Relation CreateFakeRelcacheEntry(RelFileLocator rlocator);
extern void FreeFakeRelcacheEntry(Relation fakerel);
 
extern int  read_local_xlog_page(XLogReaderState *state,
                                 XLogRecPtr targetPagePtr, int reqLen,
                                 XLogRecPtr targetRecPtr, char *cur_page);
extern int  read_local_xlog_page_no_wait(XLogReaderState *state,
                                         XLogRecPtr targetPagePtr, int reqLen,
                                         XLogRecPtr targetRecPtr,
                                         char *cur_page);
extern void wal_segment_open(XLogReaderState *state,
                             XLogSegNo nextSegNo,
                             TimeLineID *tli_p);
extern void wal_segment_close(XLogReaderState *state);
 
extern void XLogReadDetermineTimeline(XLogReaderState *state,
                                      XLogRecPtr wantPage,
                                      uint32 wantLength,
                                      TimeLineID currTLI);
 
extern void WALReadRaiseError(WALReadError *errinfo);
 
#endif