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synced 2025-07-28 23:42:10 +03:00
Clean up some awkward, inaccurate, and inefficient processing around
MaxStandbyDelay. Use the GUC units mechanism for the value, and choose more appropriate timestamp functions for performing tests with it. Make the ps_activity manipulation in ResolveRecoveryConflictWithVirtualXIDs have behavior similar to ps_activity code elsewhere, notably not updating the display when update_process_title is off and not truncating the display contents at an arbitrarily-chosen length. Improve the docs to be explicit about what MaxStandbyDelay actually measures, viz the difference between primary and standby servers' clocks, and the possible hazards if their clocks aren't in sync.
This commit is contained in:
Tom Lane
@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.407 2010/04/29 21:49:03 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.408 2010/05/02 02:10:33 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -72,7 +72,7 @@ int XLogArchiveTimeout = 0;
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bool XLogArchiveMode = false;
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char *XLogArchiveCommand = NULL;
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bool EnableHotStandby = false;
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int MaxStandbyDelay = 30;
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int MaxStandbyDelay = 30 * 1000;
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bool fullPageWrites = true;
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bool log_checkpoints = false;
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int sync_method = DEFAULT_SYNC_METHOD;
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@ -11,7 +11,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.20 2010/04/28 16:10:42 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.21 2010/05/02 02:10:33 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -124,31 +124,24 @@ static int standbyWait_us = STANDBY_INITIAL_WAIT_US;
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static bool
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WaitExceedsMaxStandbyDelay(void)
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{
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long delay_secs;
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int delay_usecs;
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if (MaxStandbyDelay == -1)
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return false;
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/* Are we past max_standby_delay? */
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TimestampDifference(GetLatestXLogTime(), GetCurrentTimestamp(),
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&delay_secs, &delay_usecs);
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if (delay_secs > MaxStandbyDelay)
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if (MaxStandbyDelay >= 0 &&
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TimestampDifferenceExceeds(GetLatestXLogTime(), GetCurrentTimestamp(),
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MaxStandbyDelay))
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return true;
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/*
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* Sleep, then do bookkeeping.
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* Sleep a bit (this is essential to avoid busy-waiting).
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*/
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pg_usleep(standbyWait_us);
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/*
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* Progressively increase the sleep times.
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* Progressively increase the sleep times, but not to more than 1s,
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* since pg_usleep isn't interruptable on some platforms.
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*/
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standbyWait_us *= 2;
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if (standbyWait_us > 1000000)
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standbyWait_us = 1000000;
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if (standbyWait_us > MaxStandbyDelay * 1000000 / 4)
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standbyWait_us = MaxStandbyDelay * 1000000 / 4;
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return false;
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}
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@ -163,50 +156,41 @@ static void
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ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
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ProcSignalReason reason)
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{
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char waitactivitymsg[100];
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char oldactivitymsg[101];
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while (VirtualTransactionIdIsValid(*waitlist))
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{
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long wait_s;
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int wait_us; /* wait in microseconds (us) */
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TimestampTz waitStart;
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bool logged;
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char *new_status;
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pgstat_report_waiting(true);
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waitStart = GetCurrentTimestamp();
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new_status = NULL; /* we haven't changed the ps display */
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/* reset standbyWait_us for each xact we wait for */
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standbyWait_us = STANDBY_INITIAL_WAIT_US;
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logged = false;
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/* wait until the virtual xid is gone */
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while (!ConditionalVirtualXactLockTableWait(*waitlist))
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{
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/*
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* Report if we have been waiting for a while now...
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* Report via ps if we have been waiting for more than 500 msec
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* (should that be configurable?)
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*/
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TimestampTz now = GetCurrentTimestamp();
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TimestampDifference(waitStart, now, &wait_s, &wait_us);
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if (!logged && (wait_s > 0 || wait_us > 500000))
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if (update_process_title && new_status == NULL &&
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TimestampDifferenceExceeds(waitStart, GetCurrentTimestamp(),
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500))
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{
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const char *oldactivitymsgp;
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const char *old_status;
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int len;
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oldactivitymsgp = get_ps_display(&len);
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if (len > 100)
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len = 100;
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memcpy(oldactivitymsg, oldactivitymsgp, len);
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oldactivitymsg[len] = 0;
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snprintf(waitactivitymsg, sizeof(waitactivitymsg),
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"waiting for max_standby_delay (%u s)",
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old_status = get_ps_display(&len);
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new_status = (char *) palloc(len + 50);
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memcpy(new_status, old_status, len);
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snprintf(new_status + len, 50,
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" waiting for max_standby_delay (%d ms)",
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MaxStandbyDelay);
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set_ps_display(waitactivitymsg, false);
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pgstat_report_waiting(true);
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logged = true;
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set_ps_display(new_status, false);
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new_status[len] = '\0'; /* truncate off " waiting" */
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}
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/* Is it time to kill it? */
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@ -225,16 +209,17 @@ ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
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* unresponsive backend when system is heavily loaded.
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*/
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if (pid != 0)
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pg_usleep(5000);
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pg_usleep(5000L);
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}
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}
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/* Reset ps display */
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if (logged)
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/* Reset ps display if we changed it */
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if (new_status)
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{
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set_ps_display(oldactivitymsg, false);
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pgstat_report_waiting(false);
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set_ps_display(new_status, false);
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pfree(new_status);
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}
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pgstat_report_waiting(false);
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/* The virtual transaction is gone now, wait for the next one */
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waitlist++;
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@ -401,7 +386,7 @@ ResolveRecoveryConflictWithBufferPin(void)
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*/
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SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
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}
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else if (MaxStandbyDelay == -1)
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else if (MaxStandbyDelay < 0)
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{
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/*
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* Send out a request to check for buffer pin deadlocks before we
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@ -412,17 +397,11 @@ ResolveRecoveryConflictWithBufferPin(void)
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}
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else
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{
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TimestampTz now;
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long standby_delay_secs; /* How far Startup process is lagging */
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int standby_delay_usecs;
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now = GetCurrentTimestamp();
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TimestampTz then = GetLatestXLogTime();
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TimestampTz now = GetCurrentTimestamp();
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/* Are we past max_standby_delay? */
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TimestampDifference(GetLatestXLogTime(), now,
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&standby_delay_secs, &standby_delay_usecs);
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if (standby_delay_secs >= MaxStandbyDelay)
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if (TimestampDifferenceExceeds(then, now, MaxStandbyDelay))
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{
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/*
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* We're already behind, so clear a path as quickly as possible.
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@ -434,7 +413,7 @@ ResolveRecoveryConflictWithBufferPin(void)
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TimestampTz fin_time; /* Expected wake-up time by timer */
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long timer_delay_secs; /* Amount of time we set timer
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* for */
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int timer_delay_usecs = 0;
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int timer_delay_usecs;
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/*
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* Send out a request to check for buffer pin deadlocks before we
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@ -446,12 +425,10 @@ ResolveRecoveryConflictWithBufferPin(void)
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/*
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* How much longer we should wait?
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*/
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timer_delay_secs = MaxStandbyDelay - standby_delay_secs;
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if (standby_delay_usecs > 0)
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{
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timer_delay_secs -= 1;
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timer_delay_usecs = 1000000 - standby_delay_usecs;
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}
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fin_time = TimestampTzPlusMilliseconds(then, MaxStandbyDelay);
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TimestampDifference(now, fin_time,
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&timer_delay_secs, &timer_delay_usecs);
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/*
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* It's possible that the difference is less than a microsecond;
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@ -460,13 +437,6 @@ ResolveRecoveryConflictWithBufferPin(void)
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if (timer_delay_secs == 0 && timer_delay_usecs == 0)
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timer_delay_usecs = 1;
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/*
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* When is the finish time? We recheck this if we are woken early.
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*/
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fin_time = TimestampTzPlusMilliseconds(now,
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(timer_delay_secs * 1000) +
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(timer_delay_usecs / 1000));
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if (enable_standby_sig_alarm(timer_delay_secs, timer_delay_usecs, fin_time))
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sig_alarm_enabled = true;
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else
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@ -10,7 +10,7 @@
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* Written by Peter Eisentraut <peter_e@gmx.net>.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.553 2010/04/29 21:36:19 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.554 2010/05/02 02:10:33 tgl Exp $
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*
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*--------------------------------------------------------------------
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*/
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@ -1386,10 +1386,11 @@ static struct config_int ConfigureNamesInt[] =
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{
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{"max_standby_delay", PGC_SIGHUP, WAL_SETTINGS,
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gettext_noop("Sets the maximum delay to avoid conflict processing on hot standby servers."),
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NULL
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NULL,
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GUC_UNIT_MS
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},
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&MaxStandbyDelay,
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30, -1, INT_MAX, NULL, NULL
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30 * 1000, -1, INT_MAX / 1000, NULL, NULL
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},
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{
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@ -186,7 +186,7 @@
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# - Hot Standby -
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#hot_standby = off # allows queries during recovery
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#max_standby_delay = 30s # max acceptable lag (s) to allow queries to
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#max_standby_delay = 30s # max acceptable lag to allow queries to
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# complete without conflict; -1 means forever
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#vacuum_defer_cleanup_age = 0 # num transactions by which cleanup is deferred
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