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Commit875d3f3

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Avoid bogus "out-of-sequence timeline ID" errors in standby-mode.
When startup process opens a WAL segment after replaying part of it, itvalidates the first page on the WAL segment, even though the page it'sreally interested in later in the file. As part of the validation, it checksthat the TLI on the page header is >= the TLI it saw on the last page itread. If the segment contains a timeline switch, and we have alreadyreplayed it, and then re-open the WAL segment (because of streamingreplication got disconnected and reconnected, for example), the TLI checkwill fail when the first page is validated. Fix that by relaxing the TLIcheck when re-opening a WAL segment.Backpatch to 9.0. Earlier versions had the same code, but before standbymode was introduced in 9.0, recovery never tried to re-read a segment afterpartially replaying it.Reported by Amit Kapila, while testing a new feature.
1 parent2a18b3e commit875d3f3

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1 file changed

+23
-9
lines changed
  • src/backend/access/transam

1 file changed

+23
-9
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 23 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -510,6 +510,7 @@ static uint32 readRecordBufSize = 0;
510510
staticXLogRecPtrReadRecPtr;/* start of last record read */
511511
staticXLogRecPtrEndRecPtr;/* end+1 of last record read */
512512
staticTimeLineIDlastPageTLI=0;
513+
staticTimeLineIDlastSegmentTLI=0;
513514

514515
staticXLogRecPtrminRecoveryPoint;/* local copy of
515516
* ControlFile->minRecoveryPoint */
@@ -596,7 +597,7 @@ static void CleanupBackupHistory(void);
596597
staticvoidUpdateMinRecoveryPoint(XLogRecPtrlsn,boolforce);
597598
staticXLogRecord*ReadRecord(XLogRecPtr*RecPtr,intemode,boolfetching_ckpt);
598599
staticvoidCheckRecoveryConsistency(void);
599-
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode);
600+
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly);
600601
staticXLogRecord*ReadCheckpointRecord(XLogRecPtrRecPtr,intwhichChkpt);
601602
staticList*readTimeLineHistory(TimeLineIDtargetTLI);
602603
staticboolexistsTimeLineHistory(TimeLineIDprobeTLI);
@@ -3742,7 +3743,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
37423743
* to go backwards (but we can't reset that variable right here, since
37433744
* we might not change files at all).
37443745
*/
3745-
lastPageTLI=0;/* see comment in ValidXLOGHeader */
3746+
lastPageTLI=lastSegmentTLI=0;/* see comment in ValidXLOGHeader */
37463747
randAccess= true;/* allow curFileTLI to go backwards too */
37473748
}
37483749

@@ -4005,7 +4006,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
40054006
* ReadRecord.It's not intended for use from anywhere else.
40064007
*/
40074008
staticbool
4008-
ValidXLOGHeader(XLogPageHeaderhdr,intemode)
4009+
ValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly)
40094010
{
40104011
XLogRecPtrrecaddr;
40114012

@@ -4100,18 +4101,31 @@ ValidXLOGHeader(XLogPageHeader hdr, int emode)
41004101
* successive pages of a consistent WAL sequence.
41014102
*
41024103
* Of course this check should only be applied when advancing sequentially
4103-
* across pages; therefore ReadRecord resets lastPageTLI to zero when
4104-
* going to a random page.
4104+
* across pages; therefore ReadRecord resets lastPageTLI and
4105+
* lastSegmentTLI to zero when going to a random page.
4106+
*
4107+
* Sometimes we re-open a segment that's already been partially replayed.
4108+
* In that case we cannot perform the normal TLI check: if there is a
4109+
* timeline switch within the segment, the first page has a smaller TLI
4110+
* than later pages following the timeline switch, and we might've read
4111+
* them already. As a weaker test, we still check that it's not smaller
4112+
* than the TLI we last saw at the beginning of a segment. Pass
4113+
* segmentonly = true when re-validating the first page like that, and the
4114+
* page you're actually interested in comes later.
41054115
*/
4106-
if (hdr->xlp_tli<lastPageTLI)
4116+
if (hdr->xlp_tli<(segmentonly ?lastSegmentTLI :lastPageTLI))
41074117
{
41084118
ereport(emode_for_corrupt_record(emode,recaddr),
41094119
(errmsg("out-of-sequence timeline ID %u (after %u) in log file %u, segment %u, offset %u",
4110-
hdr->xlp_tli,lastPageTLI,
4120+
hdr->xlp_tli,
4121+
segmentonly ?lastSegmentTLI :lastPageTLI,
41114122
readId,readSeg,readOff)));
41124123
return false;
41134124
}
41144125
lastPageTLI=hdr->xlp_tli;
4126+
if (readOff==0)
4127+
lastSegmentTLI=hdr->xlp_tli;
4128+
41154129
return true;
41164130
}
41174131

@@ -9689,7 +9703,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
96899703
readId,readSeg,readOff)));
96909704
gotonext_record_is_invalid;
96919705
}
9692-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
9706+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, true))
96939707
gotonext_record_is_invalid;
96949708
}
96959709

@@ -9711,7 +9725,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
97119725
readId,readSeg,readOff)));
97129726
gotonext_record_is_invalid;
97139727
}
9714-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
9728+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, false))
97159729
gotonext_record_is_invalid;
97169730

97179731
Assert(targetId==readId);

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