diff options
Diffstat (limited to 'src/backend/utils/time/snapmgr.c')
| -rw-r--r-- | src/backend/utils/time/snapmgr.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c index 12ca81616d1..9c06124ba95 100644 --- a/src/backend/utils/time/snapmgr.c +++ b/src/backend/utils/time/snapmgr.c @@ -19,7 +19,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/time/snapmgr.c,v 1.10.2.1 2009/10/02 17:58:21 alvherre Exp $ + * $PostgreSQL: pgsql/src/backend/utils/time/snapmgr.c,v 1.10.2.2 2009/10/07 16:27:28 alvherre Exp $ * *------------------------------------------------------------------------- */ @@ -104,6 +104,7 @@ bool FirstSnapshotSet = false; static bool registered_serializable = false; +static Snapshot CopySnapshot(Snapshot snapshot); static void FreeSnapshot(Snapshot snapshot); static void SnapshotResetXmin(void); @@ -191,7 +192,7 @@ SnapshotSetCommandId(CommandId curcid) * The copy is palloc'd in TopTransactionContext and has initial refcounts set * to 0. The returned snapshot has the copied flag set. */ -Snapshot +static Snapshot CopySnapshot(Snapshot snapshot) { Snapshot newsnap; @@ -254,8 +255,9 @@ FreeSnapshot(Snapshot snapshot) * PushActiveSnapshot * Set the given snapshot as the current active snapshot * - * If this is the first use of this snapshot, create a new long-lived copy with - * active refcount=1. Otherwise, only increment the refcount. + * If the passed snapshot is a statically-allocated one, or it is possibly + * subject to a future command counter update, create a new long-lived copy + * with active refcount=1. Otherwise, only increment the refcount. */ void PushActiveSnapshot(Snapshot snap) @@ -265,8 +267,16 @@ PushActiveSnapshot(Snapshot snap) Assert(snap != InvalidSnapshot); newactive = MemoryContextAlloc(TopTransactionContext, sizeof(ActiveSnapshotElt)); - /* Static snapshot? Create a persistent copy */ - newactive->as_snap = snap->copied ? snap : CopySnapshot(snap); + + /* + * Checking SecondarySnapshot is probably useless here, but it seems better + * to be sure. + */ + if (snap == CurrentSnapshot || snap == SecondarySnapshot || !snap->copied) + newactive->as_snap = CopySnapshot(snap); + else + newactive->as_snap = snap; + newactive->as_next = ActiveSnapshot; newactive->as_level = GetCurrentTransactionNestLevel(); |