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Commit39e98d9

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Repair sometimes-incorrect computation of StartUpID after a crash, per
example from Rao Kumar. This is a very corner corner-case, requiringa minimum of three closely-spaced database crashes and an unluckypositioning of the second recovery's checkpoint record before you'd noticeany problem. But the consequences are dire enough that it's a must-fix.
1 parentbaba071 commit39e98d9

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1 file changed

+64
-52
lines changed
  • src/backend/access/transam

1 file changed

+64
-52
lines changed

‎src/backend/access/transam/xlog.c‎

Lines changed: 64 additions & 52 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.115 2003/05/10 18:01:31 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.116 2003/05/22 14:39:28 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -2568,7 +2568,18 @@ StartupXLOG(void)
25682568
ShmemVariableCache->nextOid=checkPoint.nextOid;
25692569
ShmemVariableCache->oidCount=0;
25702570

2571-
ThisStartUpID=checkPoint.ThisStartUpID;
2571+
/*
2572+
* If it was a shutdown checkpoint, then any following WAL entries were
2573+
* created under the next StartUpID; if it was a regular checkpoint then
2574+
* any following WAL entries were created under the same StartUpID.
2575+
* We must replay WAL entries using the same StartUpID they were created
2576+
* under, so temporarily adopt that SUI (see also xlog_redo()).
2577+
*/
2578+
if (wasShutdown)
2579+
ThisStartUpID=checkPoint.ThisStartUpID+1;
2580+
else
2581+
ThisStartUpID=checkPoint.ThisStartUpID;
2582+
25722583
RedoRecPtr=XLogCtl->Insert.RedoRecPtr=
25732584
XLogCtl->SavedRedoRecPtr=checkPoint.redo;
25742585

@@ -2672,55 +2683,21 @@ StartupXLOG(void)
26722683
ControlFile->logSeg=openLogSeg+1;
26732684
Insert=&XLogCtl->Insert;
26742685
Insert->PrevRecord=LastRec;
2686+
XLogCtl->xlblocks[0].xlogid=openLogId;
2687+
XLogCtl->xlblocks[0].xrecoff=
2688+
((EndOfLog.xrecoff-1) /BLCKSZ+1)*BLCKSZ;
26752689

26762690
/*
2677-
* If the next record will go to the new page then initialize for that
2678-
* one.
2691+
* Tricky point here: readBuf contains the *last* block that the
2692+
* LastRec record spans, not the one it starts in.The last block
2693+
* is indeed the one we want to use.
26792694
*/
2680-
if ((BLCKSZ-EndOfLog.xrecoff %BLCKSZ)<SizeOfXLogRecord)
2681-
EndOfLog.xrecoff+= (BLCKSZ-EndOfLog.xrecoff %BLCKSZ);
2682-
if (EndOfLog.xrecoff %BLCKSZ==0)
2683-
{
2684-
XLogRecPtrNewPageEndPtr;
2685-
2686-
NewPageEndPtr=EndOfLog;
2687-
if (NewPageEndPtr.xrecoff >=XLogFileSize)
2688-
{
2689-
/* crossing a logid boundary */
2690-
NewPageEndPtr.xlogid+=1;
2691-
NewPageEndPtr.xrecoff=BLCKSZ;
2692-
}
2693-
else
2694-
NewPageEndPtr.xrecoff+=BLCKSZ;
2695-
XLogCtl->xlblocks[0]=NewPageEndPtr;
2696-
Insert->currpage->xlp_magic=XLOG_PAGE_MAGIC;
2697-
if (InRecovery)
2698-
Insert->currpage->xlp_sui=ThisStartUpID;
2699-
else
2700-
Insert->currpage->xlp_sui=ThisStartUpID+1;
2701-
Insert->currpage->xlp_pageaddr.xlogid=NewPageEndPtr.xlogid;
2702-
Insert->currpage->xlp_pageaddr.xrecoff=NewPageEndPtr.xrecoff-BLCKSZ;
2703-
/* rest of buffer was zeroed in XLOGShmemInit */
2704-
Insert->currpos= (char*)Insert->currpage+SizeOfXLogPHD;
2705-
}
2706-
else
2707-
{
2708-
XLogCtl->xlblocks[0].xlogid=openLogId;
2709-
XLogCtl->xlblocks[0].xrecoff=
2710-
((EndOfLog.xrecoff-1) /BLCKSZ+1)*BLCKSZ;
2711-
2712-
/*
2713-
* Tricky point here: readBuf contains the *last* block that the
2714-
* LastRec record spans, not the one it starts in.The last block
2715-
* is indeed the one we want to use.
2716-
*/
2717-
Assert(readOff== (XLogCtl->xlblocks[0].xrecoff-BLCKSZ) %XLogSegSize);
2718-
memcpy((char*)Insert->currpage,readBuf,BLCKSZ);
2719-
Insert->currpos= (char*)Insert->currpage+
2720-
(EndOfLog.xrecoff+BLCKSZ-XLogCtl->xlblocks[0].xrecoff);
2721-
/* Make sure rest of page is zero */
2722-
memset(Insert->currpos,0,INSERT_FREESPACE(Insert));
2723-
}
2695+
Assert(readOff== (XLogCtl->xlblocks[0].xrecoff-BLCKSZ) %XLogSegSize);
2696+
memcpy((char*)Insert->currpage,readBuf,BLCKSZ);
2697+
Insert->currpos= (char*)Insert->currpage+
2698+
(EndOfLog.xrecoff+BLCKSZ-XLogCtl->xlblocks[0].xrecoff);
2699+
/* Make sure rest of page is zero */
2700+
MemSet(Insert->currpos,0,INSERT_FREESPACE(Insert));
27242701

27252702
LogwrtResult.Write=LogwrtResult.Flush=EndOfLog;
27262703

@@ -2774,9 +2751,22 @@ StartupXLOG(void)
27742751
MyXactMadeXLogEntry= false;
27752752
MyXactMadeTempRelUpdate= false;
27762753

2754+
/*
2755+
* At this point, ThisStartUpID is the largest SUI that we could
2756+
* find evidence for in the WAL entries. But check it against
2757+
* pg_control's latest checkpoint, to make sure that we can't
2758+
* accidentally re-use an already-used SUI.
2759+
*/
2760+
if (ThisStartUpID<ControlFile->checkPointCopy.ThisStartUpID)
2761+
ThisStartUpID=ControlFile->checkPointCopy.ThisStartUpID;
2762+
27772763
/*
27782764
* Perform a new checkpoint to update our recovery activity to disk.
27792765
*
2766+
* Note that we write a shutdown checkpoint. This is correct since
2767+
* the records following it will use SUI one more than what is shown
2768+
* in the checkpoint's ThisStartUpID.
2769+
*
27802770
* In case we had to use the secondary checkpoint, make sure that
27812771
* it will still be shown as the secondary checkpoint after this
27822772
* CreateCheckPoint operation; we don't want the broken primary
@@ -2790,21 +2780,39 @@ StartupXLOG(void)
27902780
*/
27912781
XLogCloseRelationCache();
27922782
}
2783+
else
2784+
{
2785+
/*
2786+
* If we are not doing recovery, then we saw a checkpoint with nothing
2787+
* after it, and we can safely use StartUpID equal to one more than
2788+
* the checkpoint's SUI. But just for paranoia's sake, check against
2789+
* pg_control too.
2790+
*/
2791+
ThisStartUpID=checkPoint.ThisStartUpID;
2792+
if (ThisStartUpID<ControlFile->checkPointCopy.ThisStartUpID)
2793+
ThisStartUpID=ControlFile->checkPointCopy.ThisStartUpID;
2794+
}
27932795

27942796
/*
27952797
* Preallocate additional log files, if wanted.
27962798
*/
27972799
PreallocXlogFiles(EndOfLog);
27982800

2801+
/*
2802+
* Advance StartUpID to one more than the highest value used previously.
2803+
*/
2804+
ThisStartUpID++;
2805+
XLogCtl->ThisStartUpID=ThisStartUpID;
2806+
2807+
/*
2808+
* Okay, we're officially UP.
2809+
*/
27992810
InRecovery= false;
28002811

28012812
ControlFile->state=DB_IN_PRODUCTION;
28022813
ControlFile->time=time(NULL);
28032814
UpdateControlFile();
28042815

2805-
ThisStartUpID++;
2806-
XLogCtl->ThisStartUpID=ThisStartUpID;
2807-
28082816
/* Start up the commit log, too */
28092817
StartupCLOG();
28102818

@@ -3000,7 +3008,7 @@ CreateCheckPoint(bool shutdown, bool force)
30003008
UpdateControlFile();
30013009
}
30023010

3003-
memset(&checkPoint,0,sizeof(checkPoint));
3011+
MemSet(&checkPoint,0,sizeof(checkPoint));
30043012
checkPoint.ThisStartUpID=ThisStartUpID;
30053013
checkPoint.time=time(NULL);
30063014

@@ -3259,6 +3267,8 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
32593267
ShmemVariableCache->nextXid=checkPoint.nextXid;
32603268
ShmemVariableCache->nextOid=checkPoint.nextOid;
32613269
ShmemVariableCache->oidCount=0;
3270+
/* Any later WAL records should be run with shutdown SUI plus 1 */
3271+
ThisStartUpID=checkPoint.ThisStartUpID+1;
32623272
}
32633273
elseif (info==XLOG_CHECKPOINT_ONLINE)
32643274
{
@@ -3274,6 +3284,8 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
32743284
ShmemVariableCache->nextOid=checkPoint.nextOid;
32753285
ShmemVariableCache->oidCount=0;
32763286
}
3287+
/* Any later WAL records should be run with the then-active SUI */
3288+
ThisStartUpID=checkPoint.ThisStartUpID;
32773289
}
32783290
}
32793291

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