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Commitdda8b87

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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 parent8af60da commitdda8b87

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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
@@ -572,6 +572,7 @@ static uint32 readRecordBufSize = 0;
572572
staticXLogRecPtrReadRecPtr;/* start of last record read */
573573
staticXLogRecPtrEndRecPtr;/* end+1 of last record read */
574574
staticTimeLineIDlastPageTLI=0;
575+
staticTimeLineIDlastSegmentTLI=0;
575576

576577
staticXLogRecPtrminRecoveryPoint;/* local copy of
577578
* ControlFile->minRecoveryPoint */
@@ -655,7 +656,7 @@ static void CleanupBackupHistory(void);
655656
staticvoidUpdateMinRecoveryPoint(XLogRecPtrlsn,boolforce);
656657
staticXLogRecord*ReadRecord(XLogRecPtr*RecPtr,intemode,boolfetching_ckpt);
657658
staticvoidCheckRecoveryConsistency(void);
658-
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode);
659+
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly);
659660
staticXLogRecord*ReadCheckpointRecord(XLogRecPtrRecPtr,intwhichChkpt);
660661
staticList*readTimeLineHistory(TimeLineIDtargetTLI);
661662
staticboolexistsTimeLineHistory(TimeLineIDprobeTLI);
@@ -3949,7 +3950,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
39493950
* to go backwards (but we can't reset that variable right here, since
39503951
* we might not change files at all).
39513952
*/
3952-
lastPageTLI=0;/* see comment in ValidXLOGHeader */
3953+
lastPageTLI=lastSegmentTLI=0;/* see comment in ValidXLOGHeader */
39533954
randAccess= true;/* allow curFileTLI to go backwards too */
39543955
}
39553956

@@ -4212,7 +4213,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
42124213
* ReadRecord.It's not intended for use from anywhere else.
42134214
*/
42144215
staticbool
4215-
ValidXLOGHeader(XLogPageHeaderhdr,intemode)
4216+
ValidXLOGHeader(XLogPageHeaderhdr,intemode,boolsegmentonly)
42164217
{
42174218
XLogRecPtrrecaddr;
42184219

@@ -4307,18 +4308,31 @@ ValidXLOGHeader(XLogPageHeader hdr, int emode)
43074308
* successive pages of a consistent WAL sequence.
43084309
*
43094310
* Of course this check should only be applied when advancing sequentially
4310-
* across pages; therefore ReadRecord resets lastPageTLI to zero when
4311-
* going to a random page.
4311+
* across pages; therefore ReadRecord resets lastPageTLI and
4312+
* lastSegmentTLI to zero when going to a random page.
4313+
*
4314+
* Sometimes we re-open a segment that's already been partially replayed.
4315+
* In that case we cannot perform the normal TLI check: if there is a
4316+
* timeline switch within the segment, the first page has a smaller TLI
4317+
* than later pages following the timeline switch, and we might've read
4318+
* them already. As a weaker test, we still check that it's not smaller
4319+
* than the TLI we last saw at the beginning of a segment. Pass
4320+
* segmentonly = true when re-validating the first page like that, and the
4321+
* page you're actually interested in comes later.
43124322
*/
4313-
if (hdr->xlp_tli<lastPageTLI)
4323+
if (hdr->xlp_tli<(segmentonly ?lastSegmentTLI :lastPageTLI))
43144324
{
43154325
ereport(emode_for_corrupt_record(emode,recaddr),
43164326
(errmsg("out-of-sequence timeline ID %u (after %u) in log file %u, segment %u, offset %u",
4317-
hdr->xlp_tli,lastPageTLI,
4327+
hdr->xlp_tli,
4328+
segmentonly ?lastSegmentTLI :lastPageTLI,
43184329
readId,readSeg,readOff)));
43194330
return false;
43204331
}
43214332
lastPageTLI=hdr->xlp_tli;
4333+
if (readOff==0)
4334+
lastSegmentTLI=hdr->xlp_tli;
4335+
43224336
return true;
43234337
}
43244338

@@ -10462,7 +10476,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
1046210476
readId,readSeg,readOff)));
1046310477
gotonext_record_is_invalid;
1046410478
}
10465-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
10479+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, true))
1046610480
gotonext_record_is_invalid;
1046710481
}
1046810482

@@ -10484,7 +10498,7 @@ XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
1048410498
readId,readSeg,readOff)));
1048510499
gotonext_record_is_invalid;
1048610500
}
10487-
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode))
10501+
if (!ValidXLOGHeader((XLogPageHeader)readBuf,emode, false))
1048810502
gotonext_record_is_invalid;
1048910503

1049010504
Assert(targetId==readId);

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