waitlsn.h

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/*-------------------------------------------------------------------------
 *
 * waitlsn.h
 *    Declarations for LSN replay waiting routines.
 *
 * Copyright (c) 2024, PostgreSQL Global Development Group
 *
 * src/include/commands/waitlsn.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef WAIT_LSN_H
#define WAIT_LSN_H
 
#include "lib/pairingheap.h"
#include "postgres.h"
#include "port/atomics.h"
#include "storage/latch.h"
#include "storage/spin.h"
#include "tcop/dest.h"
 
/*
 * WaitLSNProcInfo - the shared memory structure representing information
 * about the single process, which may wait for LSN replay.  An item of
 * waitLSN->procInfos array.
 */
typedef struct WaitLSNProcInfo
{
    /* LSN, which this process is waiting for */
    XLogRecPtr  waitLSN;
 
    /*
     * A pointer to the latch, which should be set once the waitLSN is
     * replayed.
     */
    Latch      *latch;
 
    /* A pairing heap node for participation in waitLSNState->waitersHeap */
    pairingheap_node phNode;
 
    /*
     * A flag indicating that this item is present in
     * waitLSNState->waitersHeap
     */
    bool        inHeap;
} WaitLSNProcInfo;
 
/*
 * WaitLSNState - the shared memory state for the replay LSN waiting facility.
 */
typedef struct WaitLSNState
{
    /*
     * The minimum LSN value some process is waiting for.  Used for the
     * fast-path checking if we need to wake up any waiters after replaying a
     * WAL record.  Could be read lock-less.  Update protected by WaitLSNLock.
     */
    pg_atomic_uint64 minWaitedLSN;
 
    /*
     * A pairing heap of waiting processes order by LSN values (least LSN is
     * on top).  Protected by WaitLSNLock.
     */
    pairingheap waitersHeap;
 
    /*
     * An array with per-process information, indexed by the process number.
     * Protected by WaitLSNLock.
     */
    WaitLSNProcInfo procInfos[FLEXIBLE_ARRAY_MEMBER];
} WaitLSNState;
 
extern PGDLLIMPORT WaitLSNState *waitLSNState;
 
extern Size WaitLSNShmemSize(void);
extern void WaitLSNShmemInit(void);
extern void WaitLSNSetLatches(XLogRecPtr currentLSN);
extern void WaitLSNCleanup(void);
extern void WaitForLSNReplay(XLogRecPtr targetLSN, int64 timeout);
 
#endif                          /* WAIT_LSN_H */