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| author | Robert Haas <rhaas@postgresql.org> | 2017-03-23 14:08:23 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2017-03-23 14:26:31 -0400 |
| commit | ea42cc18c35381f639d45628d792e790ff39e271 (patch) | |
| tree | 223916f28189cb8fb5b40793ff563928795f62ca /src/backend/access/transam/xlog.c | |
| parent | 50c956add83963d7bbb367dd0b879fccddebd623 (diff) | |
| download | postgresql-ea42cc18c35381f639d45628d792e790ff39e271.tar.gz postgresql-ea42cc18c35381f639d45628d792e790ff39e271.zip | |
Track the oldest XID that can be safely looked up in CLOG.
This provides infrastructure for looking up arbitrary, user-supplied
XIDs without a risk of scary-looking failures from within the clog
module. Normally, the oldest XID that can be safely looked up in CLOG
is the same as the oldest XID that can reused without causing
wraparound, and the latter is already tracked. However, while
truncation is in progress, the values are different, so we must
keep track of them separately.
Craig Ringer, reviewed by Simon Riggs and by me.
Discussion: http://postgr.es/m/CAMsr+YHQiWNEi0daCTboS40T+V5s_+dst3PYv_8v2wNVH+Xx4g@mail.gmail.com
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index de1937e013d..b99ded5df67 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -5016,6 +5016,7 @@ BootStrapXLOG(void) ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); + AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(InvalidTransactionId, InvalidTransactionId); @@ -6622,6 +6623,7 @@ StartupXLOG(void) ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); + AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(checkPoint.oldestCommitTsXid, @@ -8687,6 +8689,11 @@ CreateCheckPoint(int flags) /* * Get the other info we need for the checkpoint record. + * + * We don't need to save oldestClogXid in the checkpoint, it only matters + * for the short period in which clog is being truncated, and if we crash + * during that we'll redo the clog truncation and fix up oldestClogXid + * there. */ LWLockAcquire(XidGenLock, LW_SHARED); checkPoint.nextXid = ShmemVariableCache->nextXid; @@ -9616,6 +9623,10 @@ xlog_redo(XLogReaderState *record) MultiXactAdvanceOldest(checkPoint.oldestMulti, checkPoint.oldestMultiDB); + /* + * No need to set oldestClogXid here as well; it'll be set when we + * redo an xl_clog_truncate if it changed since initialization. + */ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* |