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Re-enable max_standby_delay = -1 using deadlock detection on startup
process. If startup waits on a buffer pin we send a request to all backends to cancel themselves if they are holding the buffer pin required and they are also waiting on a lock. If not, startup waits until max_standby_delay before cancelling any backend waiting for the requested buffer pin.
This commit is contained in:
Simon Riggs
@ -8,7 +8,7 @@
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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/procsignal.c,v 1.4 2010/01/23 16:37:12 sriggs Exp $
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* $PostgreSQL: pgsql/src/backend/storage/ipc/procsignal.c,v 1.5 2010/02/13 01:32:19 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -272,6 +272,9 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
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if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT))
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RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT);
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if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK))
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RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
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if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
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RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
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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 1.11 2010/02/11 19:35:22 sriggs Exp $
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* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.12 2010/02/13 01:32:19 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -127,6 +127,9 @@ WaitExceedsMaxStandbyDelay(void)
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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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@ -351,15 +354,15 @@ ResolveRecoveryConflictWithLock(Oid dbOid, Oid relOid)
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* they hold one of the buffer pins that is blocking Startup process. If so,
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* backends will take an appropriate error action, ERROR or FATAL.
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*
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* A secondary purpose of this is to avoid deadlocks that might occur between
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* the Startup process and lock waiters. Deadlocks occur because if queries
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* We also check for deadlocks before we wait, though applications that cause
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* these will be extremely rare. Deadlocks occur because if queries
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* wait on a lock, that must be behind an AccessExclusiveLock, which can only
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* be clared if the Startup process replays a transaction completion record.
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* If Startup process is waiting then that is a deadlock. If we allowed a
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* setting of max_standby_delay that meant "wait forever" we would then need
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* special code to protect against deadlock. Such deadlocks are rare, so the
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* code would be almost certainly buggy, so we avoid both long waits and
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* deadlocks using the same mechanism.
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* be cleared if the Startup process replays a transaction completion record.
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* If Startup process is also waiting then that is a deadlock. The deadlock
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* can occur if the query is waiting and then the Startup sleeps, or if
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* Startup is sleeping and the the query waits on a lock. We protect against
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* only the former sequence here, the latter sequence is checked prior to
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* the query sleeping, in CheckRecoveryConflictDeadlock().
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*/
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void
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ResolveRecoveryConflictWithBufferPin(void)
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@ -368,11 +371,23 @@ ResolveRecoveryConflictWithBufferPin(void)
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Assert(InHotStandby);
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/*
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* Signal immediately or set alarm for later.
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*/
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if (MaxStandbyDelay == 0)
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SendRecoveryConflictWithBufferPin();
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{
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/*
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* We don't want to wait, so just tell everybody holding the pin to
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* get out of town.
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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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{
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/*
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* Send out a request to check for buffer pin deadlocks before we wait.
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* This is fairly cheap, so no need to wait for deadlock timeout before
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* trying to send it out.
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*/
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SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
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}
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else
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{
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TimestampTz now;
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@ -386,13 +401,25 @@ ResolveRecoveryConflictWithBufferPin(void)
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&standby_delay_secs, &standby_delay_usecs);
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if (standby_delay_secs >= MaxStandbyDelay)
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SendRecoveryConflictWithBufferPin();
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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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*/
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SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
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}
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else
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{
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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 for */
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int timer_delay_usecs = 0;
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/*
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* Send out a request to check for buffer pin deadlocks before we wait.
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* This is fairly cheap, so no need to wait for deadlock timeout before
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* trying to send it out.
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*/
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SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
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/*
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* How much longer we should wait?
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*/
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@ -435,15 +462,18 @@ ResolveRecoveryConflictWithBufferPin(void)
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}
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void
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SendRecoveryConflictWithBufferPin(void)
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SendRecoveryConflictWithBufferPin(ProcSignalReason reason)
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{
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Assert(reason == PROCSIG_RECOVERY_CONFLICT_BUFFERPIN ||
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reason == PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
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/*
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* We send signal to all backends to ask them if they are holding
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* the buffer pin which is delaying the Startup process. We must
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* not set the conflict flag yet, since most backends will be innocent.
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* Let the SIGUSR1 handling in each backend decide their own fate.
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*/
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CancelDBBackends(InvalidOid, PROCSIG_RECOVERY_CONFLICT_BUFFERPIN, false);
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CancelDBBackends(InvalidOid, reason, false);
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}
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/*
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.215 2010/02/08 04:33:54 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.216 2010/02/13 01:32:19 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -45,6 +45,7 @@
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#include "storage/pmsignal.h"
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#include "storage/proc.h"
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#include "storage/procarray.h"
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#include "storage/procsignal.h"
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#include "storage/spin.h"
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@ -556,6 +557,15 @@ HaveNFreeProcs(int n)
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return (n <= 0);
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}
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bool
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IsWaitingForLock(void)
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{
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if (lockAwaited == NULL)
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return false;
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return true;
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}
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/*
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* Cancel any pending wait for lock, when aborting a transaction.
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*
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@ -1670,7 +1680,7 @@ CheckStandbyTimeout(void)
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now = GetCurrentTimestamp();
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if (now >= statement_fin_time)
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SendRecoveryConflictWithBufferPin();
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SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
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else
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{
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/* Not time yet, so (re)schedule the interrupt */
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.587 2010/01/23 17:04:05 sriggs Exp $
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* $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.588 2010/02/13 01:32:19 sriggs Exp $
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*
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* NOTES
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* this is the "main" module of the postgres backend and
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@ -2278,6 +2278,9 @@ errdetail_recovery_conflict(void)
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case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
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errdetail("User query might have needed to see row versions that must be removed.");
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break;
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case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
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errdetail("User transaction caused buffer deadlock with recovery.");
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break;
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case PROCSIG_RECOVERY_CONFLICT_DATABASE:
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errdetail("User was connected to a database that must be dropped.");
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break;
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@ -2754,6 +2757,15 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
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RecoveryConflictReason = reason;
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switch (reason)
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{
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case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
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/*
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* If we aren't waiting for a lock we can never deadlock.
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*/
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if (!IsWaitingForLock())
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return;
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/* Intentional drop through to check wait for pin */
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case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:
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/*
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* If we aren't blocking the Startup process there is
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@ -2819,6 +2831,8 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
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elog(FATAL, "Unknown conflict mode");
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}
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Assert(RecoveryConflictPending && (QueryCancelPending || ProcDiePending));
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/*
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* If it's safe to interrupt, and we're waiting for input or a lock,
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* service the interrupt immediately
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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 1.538 2010/02/01 13:40:28 sriggs Exp $
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.539 2010/02/13 01:32:20 sriggs Exp $
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*
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*--------------------------------------------------------------------
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*/
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@ -1381,7 +1381,7 @@ static struct config_int ConfigureNamesInt[] =
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NULL
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},
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&MaxStandbyDelay,
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30, 0, INT_MAX, NULL, NULL
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30, -1, INT_MAX, NULL, NULL
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},
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{
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@ -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/include/storage/proc.h,v 1.119 2010/01/23 16:37:12 sriggs Exp $
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* $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.120 2010/02/13 01:32:20 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -189,6 +189,7 @@ extern void ProcQueueInit(PROC_QUEUE *queue);
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extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable);
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extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus);
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extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock);
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extern bool IsWaitingForLock(void);
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extern void LockWaitCancel(void);
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extern void ProcWaitForSignal(void);
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@ -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/include/storage/procsignal.h,v 1.4 2010/01/23 16:37:12 sriggs Exp $
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* $PostgreSQL: pgsql/src/include/storage/procsignal.h,v 1.5 2010/02/13 01:32:20 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -38,6 +38,7 @@ typedef enum
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PROCSIG_RECOVERY_CONFLICT_LOCK,
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PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
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PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
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PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK,
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NUM_PROCSIGNALS /* Must be last! */
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} ProcSignalReason;
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@ -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/include/storage/standby.h,v 1.7 2010/01/31 19:01:11 sriggs Exp $
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* $PostgreSQL: pgsql/src/include/storage/standby.h,v 1.8 2010/02/13 01:32:20 sriggs Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -16,6 +16,7 @@
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#include "access/xlog.h"
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#include "storage/lock.h"
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#include "storage/procsignal.h"
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#include "storage/relfilenode.h"
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extern int vacuum_defer_cleanup_age;
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@ -30,7 +31,7 @@ extern void ResolveRecoveryConflictWithTablespace(Oid tsid);
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extern void ResolveRecoveryConflictWithDatabase(Oid dbid);
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extern void ResolveRecoveryConflictWithBufferPin(void);
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extern void SendRecoveryConflictWithBufferPin(void);
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extern void SendRecoveryConflictWithBufferPin(ProcSignalReason reason);
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extern void CheckRecoveryConflictDeadlock(LWLockId partitionLock);
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/*
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