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/*-------------------------------------------------------------------------
*
* xlogwait.h
* Declarations for LSN replay waiting routines.
*
* Copyright (c) 2025, PostgreSQL Global Development Group
*
* src/include/access/xlogwait.h
*
*-------------------------------------------------------------------------
*/
#ifndef XLOG_WAIT_H
#define XLOG_WAIT_H
#include "access/xlogdefs.h"
#include "lib/pairingheap.h"
#include "port/atomics.h"
#include "storage/procnumber.h"
#include "storage/spin.h"
#include "tcop/dest.h"
/*
* Result statuses for WaitForLSNReplay().
*/
typedef enum
{
WAIT_LSN_RESULT_SUCCESS, /* Target LSN is reached */
WAIT_LSN_RESULT_NOT_IN_RECOVERY, /* Recovery ended before or during our
* wait */
WAIT_LSN_RESULT_TIMEOUT /* Timeout occurred */
} WaitLSNResult;
/*
* LSN type for waiting facility.
*/
typedef enum WaitLSNType
{
WAIT_LSN_TYPE_REPLAY = 0, /* Waiting for replay on standby */
WAIT_LSN_TYPE_FLUSH = 1, /* Waiting for flush on primary */
WAIT_LSN_TYPE_COUNT = 2
} WaitLSNType;
/*
* WaitLSNProcInfo - the shared memory structure representing information
* about the single process, which may wait for LSN operations. An item of
* waitLSNState->procInfos array.
*/
typedef struct WaitLSNProcInfo
{
/* LSN, which this process is waiting for */
XLogRecPtr waitLSN;
/* Process to wake up once the waitLSN is reached */
ProcNumber procno;
/* Heap membership flags for LSN types */
bool inHeap[WAIT_LSN_TYPE_COUNT];
/* Heap nodes for LSN types */
pairingheap_node heapNode[WAIT_LSN_TYPE_COUNT];
} WaitLSNProcInfo;
/*
* WaitLSNState - the shared memory state for the LSN waiting facility.
*/
typedef struct WaitLSNState
{
/*
* The minimum LSN values 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[WAIT_LSN_TYPE_COUNT];
/*
* A pairing heaps of waiting processes ordered by LSN values (least LSN
* is on top). Protected by WaitLSNLock.
*/
pairingheap waitersHeap[WAIT_LSN_TYPE_COUNT];
/*
* 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 WaitLSNWakeup(WaitLSNType lsnType, XLogRecPtr currentLSN);
extern void WaitLSNCleanup(void);
extern WaitLSNResult WaitForLSN(WaitLSNType lsnType, XLogRecPtr targetLSN,
int64 timeout);
#endif /* XLOG_WAIT_H */
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