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Commit531d21b

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Cleanup commit timestamp module activaction, again
Further tweak commit_ts.c so that on a standby the state is completelyconsistent with what that in the master, rather than behavingdifferently in the cases that the settings differ. Now in standby andmaster the module should always be active or inactive in lockstep.Author: Petr Jelínek, with some further tweaks by Álvaro Herrera.Backpatch to 9.5, where commit timestamps were introduced.Discussion:http://www.postgresql.org/message-id/5622BF9D.2010409@2ndquadrant.com
1 parent0cd836a commit531d21b

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3 files changed

+81
-72
lines changed

3 files changed

+81
-72
lines changed

‎src/backend/access/transam/commit_ts.c

Lines changed: 79 additions & 70 deletions
Original file line numberDiff line numberDiff line change
@@ -78,13 +78,21 @@ static SlruCtlData CommitTsCtlData;
7878
#defineCommitTsCtl (&CommitTsCtlData)
7979

8080
/*
81-
* We keep a cache of the last value set in shared memory. This is protected
82-
* by CommitTsLock.
81+
* We keep a cache of the last value set in shared memory.
82+
*
83+
* This is also good place to keep the activation status. We keep this
84+
* separate from the GUC so that the standby can activate the module if the
85+
* primary has it active independently of the value of the GUC.
86+
*
87+
* This is protected by CommitTsLock. In some places, we use commitTsActive
88+
* without acquiring the lock; where this happens, a comment explains the
89+
* rationale for it.
8390
*/
8491
typedefstructCommitTimestampShared
8592
{
8693
TransactionIdxidLastCommit;
8794
CommitTimestampEntrydataLastCommit;
95+
boolcommitTsActive;
8896
}CommitTimestampShared;
8997

9098
CommitTimestampShared*commitTsShared;
@@ -93,14 +101,6 @@ CommitTimestampShared *commitTsShared;
93101
/* GUC variable */
94102
booltrack_commit_timestamp;
95103

96-
/*
97-
* When this is set, commit_ts is force-enabled during recovery. This is so
98-
* that a standby can replay WAL records coming from a master with the setting
99-
* enabled. (Note that this doesn't enable SQL access to the data; it's
100-
* effectively write-only until the GUC itself is enabled.)
101-
*/
102-
staticboolenable_during_recovery;
103-
104104
staticvoidSetXidCommitTsInPage(TransactionIdxid,intnsubxids,
105105
TransactionId*subxids,TimestampTzts,
106106
RepOriginIdnodeid,intpageno);
@@ -109,7 +109,7 @@ static void TransactionIdSetCommitTs(TransactionId xid, TimestampTz ts,
109109
staticintZeroCommitTsPage(intpageno,boolwriteXlog);
110110
staticboolCommitTsPagePrecedes(intpage1,intpage2);
111111
staticvoidActivateCommitTs(void);
112-
staticvoidDeactivateCommitTs(booldo_wal);
112+
staticvoidDeactivateCommitTs(void);
113113
staticvoidWriteZeroPageXlogRec(intpageno);
114114
staticvoidWriteTruncateXlogRec(intpageno);
115115
staticvoidWriteSetTimestampXlogRec(TransactionIdmainxid,intnsubxids,
@@ -149,10 +149,14 @@ TransactionTreeSetCommitTsData(TransactionId xid, int nsubxids,
149149
TransactionIdnewestXact;
150150

151151
/*
152-
* No-op if the module is not enabled, but allow writes in a standby
153-
* during recovery.
152+
* No-op if the module is not active.
153+
*
154+
* An unlocked read here is fine, because in a standby (the only place
155+
* where the flag can change in flight) this routine is only called by
156+
* the recovery process, which is also the only process which can change
157+
* the flag.
154158
*/
155-
if (!track_commit_timestamp&& !enable_during_recovery)
159+
if (!commitTsShared->commitTsActive)
156160
return;
157161

158162
/*
@@ -283,30 +287,45 @@ TransactionIdGetCommitTsData(TransactionId xid, TimestampTz *ts,
283287
TransactionIdoldestCommitTs;
284288
TransactionIdnewestCommitTs;
285289

290+
/* error if the given Xid doesn't normally commit */
291+
if (!TransactionIdIsNormal(xid))
292+
ereport(ERROR,
293+
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
294+
errmsg("cannot retrieve commit timestamp for transaction %u",xid)));
295+
296+
LWLockAcquire(CommitTsLock,LW_SHARED);
297+
286298
/* Error if module not enabled */
287-
if (!track_commit_timestamp)
299+
if (!commitTsShared->commitTsActive)
288300
ereport(ERROR,
289301
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
290302
errmsg("could not get commit timestamp data"),
291303
errhint("Make sure the configuration parameter \"%s\" is set.",
292304
"track_commit_timestamp")));
293305

294-
/* error if the given Xid doesn't normally commit */
295-
if (!TransactionIdIsNormal(xid))
296-
ereport(ERROR,
297-
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
298-
errmsg("cannot retrieve commit timestamp for transaction %u",xid)));
299-
300306
/*
301-
* Return empty if the requested value is outside our valid range.
307+
* If we're asked for the cached value, return that. Otherwise, fall
308+
* through to read from SLRU.
302309
*/
303-
LWLockAcquire(CommitTsLock,LW_SHARED);
310+
if (commitTsShared->xidLastCommit==xid)
311+
{
312+
*ts=commitTsShared->dataLastCommit.time;
313+
if (nodeid)
314+
*nodeid=commitTsShared->dataLastCommit.nodeid;
315+
316+
LWLockRelease(CommitTsLock);
317+
return*ts!=0;
318+
}
319+
304320
oldestCommitTs=ShmemVariableCache->oldestCommitTs;
305321
newestCommitTs=ShmemVariableCache->newestCommitTs;
306322
/* neither is invalid, or both are */
307323
Assert(TransactionIdIsValid(oldestCommitTs)==TransactionIdIsValid(newestCommitTs));
308324
LWLockRelease(CommitTsLock);
309325

326+
/*
327+
* Return empty if the requested value is outside our valid range.
328+
*/
310329
if (!TransactionIdIsValid(oldestCommitTs)||
311330
TransactionIdPrecedes(xid,oldestCommitTs)||
312331
TransactionIdPrecedes(newestCommitTs,xid))
@@ -317,27 +336,6 @@ TransactionIdGetCommitTsData(TransactionId xid, TimestampTz *ts,
317336
return false;
318337
}
319338

320-
/*
321-
* Use an unlocked atomic read on our cached value in shared memory; if
322-
* it's a hit, acquire a lock and read the data, after verifying that it's
323-
* still what we initially read. Otherwise, fall through to read from
324-
* SLRU.
325-
*/
326-
if (commitTsShared->xidLastCommit==xid)
327-
{
328-
LWLockAcquire(CommitTsLock,LW_SHARED);
329-
if (commitTsShared->xidLastCommit==xid)
330-
{
331-
*ts=commitTsShared->dataLastCommit.time;
332-
if (nodeid)
333-
*nodeid=commitTsShared->dataLastCommit.nodeid;
334-
335-
LWLockRelease(CommitTsLock);
336-
return*ts!=0;
337-
}
338-
LWLockRelease(CommitTsLock);
339-
}
340-
341339
/* lock is acquired by SimpleLruReadPage_ReadOnly */
342340
slotno=SimpleLruReadPage_ReadOnly(CommitTsCtl,pageno,xid);
343341
memcpy(&entry,
@@ -366,15 +364,16 @@ GetLatestCommitTsData(TimestampTz *ts, RepOriginId *nodeid)
366364
{
367365
TransactionIdxid;
368366

367+
LWLockAcquire(CommitTsLock,LW_SHARED);
368+
369369
/* Error if module not enabled */
370-
if (!track_commit_timestamp)
370+
if (!commitTsShared->commitTsActive)
371371
ereport(ERROR,
372372
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
373373
errmsg("could not get commit timestamp data"),
374374
errhint("Make sure the configuration parameter \"%s\" is set.",
375375
"track_commit_timestamp")));
376376

377-
LWLockAcquire(CommitTsLock,LW_SHARED);
378377
xid=commitTsShared->xidLastCommit;
379378
if (ts)
380379
*ts=commitTsShared->dataLastCommit.time;
@@ -493,6 +492,7 @@ CommitTsShmemInit(void)
493492
commitTsShared->xidLastCommit=InvalidTransactionId;
494493
TIMESTAMP_NOBEGIN(commitTsShared->dataLastCommit.time);
495494
commitTsShared->dataLastCommit.nodeid=InvalidRepOriginId;
495+
commitTsShared->commitTsActive= false;
496496
}
497497
else
498498
Assert(found);
@@ -566,7 +566,7 @@ CompleteCommitTsInitialization(void)
566566
* any leftover data.
567567
*/
568568
if (!track_commit_timestamp)
569-
DeactivateCommitTs(true);
569+
DeactivateCommitTs();
570570
}
571571

572572
/*
@@ -588,11 +588,11 @@ CommitTsParameterChange(bool newvalue, bool oldvalue)
588588
*/
589589
if (newvalue)
590590
{
591-
if (!track_commit_timestamp&& !oldvalue)
591+
if (!commitTsShared->commitTsActive)
592592
ActivateCommitTs();
593593
}
594-
elseif (!track_commit_timestamp&&oldvalue)
595-
DeactivateCommitTs(false);
594+
elseif (commitTsShared->commitTsActive)
595+
DeactivateCommitTs();
596596
}
597597

598598
/*
@@ -645,7 +645,7 @@ ActivateCommitTs(void)
645645
}
646646
LWLockRelease(CommitTsLock);
647647

648-
/*Finally, create the current segment file, if necessary */
648+
/*Create the current segment file, if necessary */
649649
if (!SimpleLruDoesPhysicalPageExist(CommitTsCtl,pageno))
650650
{
651651
intslotno;
@@ -657,8 +657,10 @@ ActivateCommitTs(void)
657657
LWLockRelease(CommitTsControlLock);
658658
}
659659

660-
/* We can now replay xlog records from this module */
661-
enable_during_recovery= true;
660+
/* Change the activation status in shared memory. */
661+
LWLockAcquire(CommitTsLock,LW_EXCLUSIVE);
662+
commitTsShared->commitTsActive= true;
663+
LWLockRelease(CommitTsLock);
662664
}
663665

664666
/*
@@ -672,21 +674,25 @@ ActivateCommitTs(void)
672674
* possibly-invalid data; also removes segments of old data.
673675
*/
674676
staticvoid
675-
DeactivateCommitTs(booldo_wal)
677+
DeactivateCommitTs(void)
676678
{
677-
TransactionIdxid=ShmemVariableCache->nextXid;
678-
intpageno=TransactionIdToCTsPage(xid);
679-
680679
/*
681-
* Re-Initialize our idea of the latest page number.
680+
* Cleanup the status in the shared memory.
681+
*
682+
* We reset everything in the commitTsShared record to prevent user from
683+
* getting confusing data about last committed transaction on the standby
684+
* when the module was activated repeatedly on the primary.
682685
*/
683-
LWLockAcquire(CommitTsControlLock,LW_EXCLUSIVE);
684-
CommitTsCtl->shared->latest_page_number=pageno;
685-
LWLockRelease(CommitTsControlLock);
686-
687686
LWLockAcquire(CommitTsLock,LW_EXCLUSIVE);
687+
688+
commitTsShared->commitTsActive= false;
689+
commitTsShared->xidLastCommit=InvalidTransactionId;
690+
TIMESTAMP_NOBEGIN(commitTsShared->dataLastCommit.time);
691+
commitTsShared->dataLastCommit.nodeid=InvalidRepOriginId;
692+
688693
ShmemVariableCache->oldestCommitTs=InvalidTransactionId;
689694
ShmemVariableCache->newestCommitTs=InvalidTransactionId;
695+
690696
LWLockRelease(CommitTsLock);
691697

692698
/*
@@ -697,10 +703,9 @@ DeactivateCommitTs(bool do_wal)
697703
* be overwritten anyway when we wrap around, but it seems better to be
698704
* tidy.)
699705
*/
706+
LWLockAcquire(CommitTsControlLock,LW_EXCLUSIVE);
700707
(void)SlruScanDirectory(CommitTsCtl,SlruScanDirCbDeleteAll,NULL);
701-
702-
/* No longer enabled on recovery */
703-
enable_during_recovery= false;
708+
LWLockRelease(CommitTsControlLock);
704709
}
705710

706711
/*
@@ -739,8 +744,13 @@ ExtendCommitTs(TransactionId newestXact)
739744
{
740745
intpageno;
741746

742-
/* nothing to do if module not enabled */
743-
if (!track_commit_timestamp&& !enable_during_recovery)
747+
/*
748+
* Nothing to do if module not enabled. Note we do an unlocked read of the
749+
* flag here, which is okay because this routine is only called from
750+
* GetNewTransactionId, which is never called in a standby.
751+
*/
752+
Assert(!InRecovery);
753+
if (!commitTsShared->commitTsActive)
744754
return;
745755

746756
/*
@@ -768,7 +778,7 @@ ExtendCommitTs(TransactionId newestXact)
768778
* Note that we don't need to flush XLOG here.
769779
*/
770780
void
771-
TruncateCommitTs(TransactionIdoldestXact,booldo_wal)
781+
TruncateCommitTs(TransactionIdoldestXact)
772782
{
773783
intcutoffPage;
774784

@@ -784,8 +794,7 @@ TruncateCommitTs(TransactionId oldestXact, bool do_wal)
784794
return;/* nothing to remove */
785795

786796
/* Write XLOG record */
787-
if (do_wal)
788-
WriteTruncateXlogRec(cutoffPage);
797+
WriteTruncateXlogRec(cutoffPage);
789798

790799
/* Now we can remove the old CommitTs segment(s) */
791800
SimpleLruTruncate(CommitTsCtl,cutoffPage);

‎src/backend/commands/vacuum.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1140,7 +1140,7 @@ vac_truncate_clog(TransactionId frozenXID,
11401140
* Truncate CLOG, multixact and CommitTs to the oldest computed value.
11411141
*/
11421142
TruncateCLOG(frozenXID);
1143-
TruncateCommitTs(frozenXID, true);
1143+
TruncateCommitTs(frozenXID);
11441144
TruncateMultiXact(minMulti,minmulti_datoid);
11451145

11461146
/*

‎src/include/access/commit_ts.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -40,7 +40,7 @@ extern void CompleteCommitTsInitialization(void);
4040
externvoidShutdownCommitTs(void);
4141
externvoidCheckPointCommitTs(void);
4242
externvoidExtendCommitTs(TransactionIdnewestXact);
43-
externvoidTruncateCommitTs(TransactionIdoldestXact,booldo_wal);
43+
externvoidTruncateCommitTs(TransactionIdoldestXact);
4444
externvoidSetCommitTsLimit(TransactionIdoldestXact,
4545
TransactionIdnewestXact);
4646
externvoidAdvanceOldestCommitTs(TransactionIdoldestXact);

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