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7a39f43d88
Add support for waiting on WAL write and flush LSNs in addition to the existing replay LSN wait type. This provides the foundation for extending the WAIT FOR command with MODE parameter. Key changes are following. - Add WAIT_LSN_TYPE_STANDBY_WRITE and WAIT_LSN_TYPE_STANDBY_FLUSH to WaitLSNType. - Add GetCurrentLSNForWaitType() to retrieve the current LSN for each wait type. - Add new wait events WAIT_EVENT_WAIT_FOR_WAL_WRITE and WAIT_EVENT_WAIT_FOR_WAL_FLUSH for pg_stat_activity visibility. - Update WaitForLSN() to use GetCurrentLSNForWaitType() internally. Discussion: https://postgr.es/m/CABPTF7UiArgW-sXj9CNwRzUhYOQrevLzkYcgBydmX5oDes1sjg%40mail.gmail.com Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Alvaro Herrera <alvherre@kurilemu.de>
112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* xlogwait.h
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* Declarations for WAL flush, write, and replay waiting routines.
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*
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* Copyright (c) 2025-2026, PostgreSQL Global Development Group
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*
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* src/include/access/xlogwait.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef XLOG_WAIT_H
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#define XLOG_WAIT_H
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#include "access/xlogdefs.h"
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#include "lib/pairingheap.h"
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#include "port/atomics.h"
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#include "storage/procnumber.h"
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#include "storage/spin.h"
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#include "tcop/dest.h"
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/*
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* Result statuses for WaitForLSN().
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*/
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typedef enum
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{
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WAIT_LSN_RESULT_SUCCESS, /* Target LSN is reached */
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WAIT_LSN_RESULT_NOT_IN_RECOVERY, /* Recovery ended before or during our
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* wait */
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WAIT_LSN_RESULT_TIMEOUT /* Timeout occurred */
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} WaitLSNResult;
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/*
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* LSN type for waiting facility.
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*/
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typedef enum WaitLSNType
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{
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/* Standby wait types (walreceiver/startup wakes) */
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WAIT_LSN_TYPE_STANDBY_REPLAY,
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WAIT_LSN_TYPE_STANDBY_WRITE,
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WAIT_LSN_TYPE_STANDBY_FLUSH,
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/* Primary wait types (WAL writer/backends wake) */
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WAIT_LSN_TYPE_PRIMARY_FLUSH,
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} WaitLSNType;
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#define WAIT_LSN_TYPE_COUNT (WAIT_LSN_TYPE_PRIMARY_FLUSH + 1)
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/*
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* WaitLSNProcInfo - the shared memory structure representing information
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* about the single process, which may wait for LSN operations. An item of
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* waitLSNState->procInfos array.
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*/
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typedef struct WaitLSNProcInfo
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{
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/* LSN, which this process is waiting for */
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XLogRecPtr waitLSN;
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/* The type of LSN to wait */
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WaitLSNType lsnType;
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/* Process to wake up once the waitLSN is reached */
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ProcNumber procno;
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/*
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* Heap membership flag. A process can wait for only one LSN type at a
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* time, so a single flag suffices (tracked by the lsnType field).
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*/
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bool inHeap;
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/* Pairing heap node for the waiters' heap (one per process) */
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pairingheap_node heapNode;
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} WaitLSNProcInfo;
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/*
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* WaitLSNState - the shared memory state for the LSN waiting facility.
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*/
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typedef struct WaitLSNState
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{
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/*
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* The minimum LSN values some process is waiting for. Used for the
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* fast-path checking if we need to wake up any waiters after replaying a
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* WAL record. Could be read lock-less. Update protected by WaitLSNLock.
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*/
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pg_atomic_uint64 minWaitedLSN[WAIT_LSN_TYPE_COUNT];
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/*
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* A pairing heaps of waiting processes ordered by LSN values (least LSN
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* is on top). Protected by WaitLSNLock.
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*/
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pairingheap waitersHeap[WAIT_LSN_TYPE_COUNT];
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/*
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* An array with per-process information, indexed by the process number.
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* Protected by WaitLSNLock.
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*/
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WaitLSNProcInfo procInfos[FLEXIBLE_ARRAY_MEMBER];
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} WaitLSNState;
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extern PGDLLIMPORT WaitLSNState *waitLSNState;
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extern Size WaitLSNShmemSize(void);
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extern void WaitLSNShmemInit(void);
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extern XLogRecPtr GetCurrentLSNForWaitType(WaitLSNType lsnType);
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extern void WaitLSNWakeup(WaitLSNType lsnType, XLogRecPtr currentLSN);
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extern void WaitLSNCleanup(void);
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extern WaitLSNResult WaitForLSN(WaitLSNType lsnType, XLogRecPtr targetLSN,
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int64 timeout);
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#endif /* XLOG_WAIT_H */
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