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Commitdb3658b

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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 parent866f2dd commitdb3658b

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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
@@ -550,6 +550,7 @@ static uint32 readRecordBufSize = 0;
550550
staticXLogRecPtrReadRecPtr;/* start of last record read */
551551
staticXLogRecPtrEndRecPtr;/* end+1 of last record read */
552552
staticTimeLineIDlastPageTLI=0;
553+
staticTimeLineIDlastSegmentTLI=0;
553554

554555
staticXLogRecPtrminRecoveryPoint;/* local copy of
555556
* ControlFile->minRecoveryPoint */
@@ -647,7 +648,7 @@ static void CleanupBackupHistory(void);
647648
staticvoidUpdateMinRecoveryPoint(XLogRecPtrlsn,boolforce);
648649
staticXLogRecord*ReadRecord(XLogRecPtr*RecPtr,intemode,boolfetching_ckpt);
649650
staticvoidCheckRecoveryConsistency(void);
650-
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode);
651+
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly);
651652
staticXLogRecord*ReadCheckpointRecord(XLogRecPtrRecPtr,intwhichChkpt);
652653
staticList*readTimeLineHistory(TimeLineIDtargetTLI);
653654
staticboolexistsTimeLineHistory(TimeLineIDprobeTLI);
@@ -3803,7 +3804,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
38033804
* to go backwards (but we can't reset that variable right here, since
38043805
* we might not change files at all).
38053806
*/
3806-
lastPageTLI=0;/* see comment in ValidXLOGHeader */
3807+
lastPageTLI=lastSegmentTLI=0;/* see comment in ValidXLOGHeader */
38073808
randAccess= true;/* allow curFileTLI to go backwards too */
38083809
}
38093810

@@ -4066,7 +4067,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
40664067
* ReadRecord.It's not intended for use from anywhere else.
40674068
*/
40684069
staticbool
4069-
ValidXLOGHeader(XLogPageHeaderhdr,intemode)
4070+
ValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly)
40704071
{
40714072
XLogRecPtrrecaddr;
40724073

@@ -4161,18 +4162,31 @@ ValidXLOGHeader(XLogPageHeader hdr, int emode)
41614162
* successive pages of a consistent WAL sequence.
41624163
*
41634164
* Of course this check should only be applied when advancing sequentially
4164-
* across pages; therefore ReadRecord resets lastPageTLI to zero when
4165-
* going to a random page.
4165+
* across pages; therefore ReadRecord resets lastPageTLI and
4166+
* lastSegmentTLI to zero when going to a random page.
4167+
*
4168+
* Sometimes we re-open a segment that's already been partially replayed.
4169+
* In that case we cannot perform the normal TLI check: if there is a
4170+
* timeline switch within the segment, the first page has a smaller TLI
4171+
* than later pages following the timeline switch, and we might've read
4172+
* them already. As a weaker test, we still check that it's not smaller
4173+
* than the TLI we last saw at the beginning of a segment. Pass
4174+
* segmentonly = true when re-validating the first page like that, and the
4175+
* page you're actually interested in comes later.
41664176
*/
4167-
if (hdr->xlp_tli<lastPageTLI)
4177+
if (hdr->xlp_tli<(segmentonly ?lastSegmentTLI :lastPageTLI))
41684178
{
41694179
ereport(emode_for_corrupt_record(emode,recaddr),
41704180
(errmsg("out-of-sequence timeline ID %u (after %u) in log file %u, segment %u, offset %u",
4171-
hdr->xlp_tli,lastPageTLI,
4181+
hdr->xlp_tli,
4182+
segmentonly ?lastSegmentTLI :lastPageTLI,
41724183
readId,readSeg,readOff)));
41734184
return false;
41744185
}
41754186
lastPageTLI=hdr->xlp_tli;
4187+
if (readOff==0)
4188+
lastSegmentTLI=hdr->xlp_tli;
4189+
41764190
return true;
41774191
}
41784192

@@ -10456,7 +10470,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
1045610470
readId,readSeg,readOff)));
1045710471
gotonext_record_is_invalid;
1045810472
}
10459-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
10473+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, true))
1046010474
gotonext_record_is_invalid;
1046110475
}
1046210476

@@ -10478,7 +10492,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
1047810492
readId,readSeg,readOff)));
1047910493
gotonext_record_is_invalid;
1048010494
}
10481-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
10495+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, false))
1048210496
gotonext_record_is_invalid;
1048310497

1048410498
Assert(targetId==readId);

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