diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/xact.c | 6 | ||||
| -rw-r--r-- | src/backend/utils/time/snapmgr.c | 21 | ||||
| -rw-r--r-- | src/include/utils/snapmgr.h | 2 |
3 files changed, 22 insertions, 7 deletions
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index c8751c697d4..cc11177bce0 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -2137,7 +2137,7 @@ CommitTransaction(void) AtEOXact_ComboCid(); AtEOXact_HashTables(true); AtEOXact_PgStat(true); - AtEOXact_Snapshot(true); + AtEOXact_Snapshot(true, false); AtCommit_ApplyLauncher(); pgstat_report_xact_timestamp(0); @@ -2409,7 +2409,7 @@ PrepareTransaction(void) AtEOXact_ComboCid(); AtEOXact_HashTables(true); /* don't call AtEOXact_PgStat here; we fixed pgstat state above */ - AtEOXact_Snapshot(true); + AtEOXact_Snapshot(true, true); pgstat_report_xact_timestamp(0); CurrentResourceOwner = NULL; @@ -2640,7 +2640,7 @@ CleanupTransaction(void) * do abort cleanup processing */ AtCleanup_Portals(); /* now safe to release portal memory */ - AtEOXact_Snapshot(false); /* and release the transaction's snapshots */ + AtEOXact_Snapshot(false, false); /* and release the transaction's snapshots */ CurrentResourceOwner = NULL; /* and resource owner */ if (TopTransactionResourceOwner) diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c index ecc32cb3fe7..67f3e2d667d 100644 --- a/src/backend/utils/time/snapmgr.c +++ b/src/backend/utils/time/snapmgr.c @@ -954,7 +954,12 @@ xmin_cmp(const pairingheap_node *a, const pairingheap_node *b, void *arg) * * If there are no more snapshots, we can reset our PGXACT->xmin to InvalidXid. * Note we can do this without locking because we assume that storing an Xid - * is atomic. + * is atomic. We do this because it will allow multi-statement transactions to + * reset their xmin and prevent us from holding back removal of dead rows; + * this has little purpose when we are dealing with very fast statements in + * read committed mode since the xmin will advance quickly anyway. It has no + * use at all when we are running single statement transactions since the xmin + * is reset as part of end of transaction anyway. * * Even if there are some remaining snapshots, we may be able to advance our * PGXACT->xmin to some degree. This typically happens when a portal is @@ -1051,7 +1056,7 @@ AtSubAbort_Snapshot(int level) * Snapshot manager's cleanup function for end of transaction */ void -AtEOXact_Snapshot(bool isCommit) +AtEOXact_Snapshot(bool isCommit, bool isPrepare) { /* * In transaction-snapshot mode we must release our privately-managed @@ -1136,7 +1141,17 @@ AtEOXact_Snapshot(bool isCommit) FirstSnapshotSet = false; - SnapshotResetXmin(); + /* + * During normal commit and abort processing, we call + * ProcArrayEndTransaction() or ProcArrayClearTransaction() to + * reset the PgXact->xmin. That call happens prior to the call to + * AtEOXact_Snapshot(), so we need not touch xmin here at all, + * accept when we are preparing a transaction. + */ + if (isPrepare) + SnapshotResetXmin(); + + Assert(MyPgXact->xmin == 0); } diff --git a/src/include/utils/snapmgr.h b/src/include/utils/snapmgr.h index 86c48d9c8ef..2f8d4fd4a0c 100644 --- a/src/include/utils/snapmgr.h +++ b/src/include/utils/snapmgr.h @@ -85,7 +85,7 @@ extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner); extern void AtSubCommit_Snapshot(int level); extern void AtSubAbort_Snapshot(int level); -extern void AtEOXact_Snapshot(bool isCommit); +extern void AtEOXact_Snapshot(bool isCommit, bool isPrepare); extern void ImportSnapshot(const char *idstr); extern bool XactHasExportedSnapshots(void); |