Fix a couple of snapshot management bugs in the new ResourceOwner world:

non-writable large objects need to have their snapshots registered on the
transaction resowner, not the current portal's, because it must persist until
the large object is closed (which the portal does not).  Also, ensure that the
serializable snapshot is recorded by the transaction resource owner too, even
when a subtransaction has changed the current resource owner before
serializable is taken.

Per bug reports from Pavan Deolasee.

1 files changed, 54 insertions, 14 deletions

diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
index 1107abdf27a..d37dc5df84c 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 1.7 2008/11/25 20:28:29 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/time/snapmgr.c,v 1.8 2008/12/04 14:51:02 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -136,7 +136,8 @@ GetTransactionSnapshot(void)
 		 */
 		if (IsXactIsoLevelSerializable)
 		{
-			CurrentSnapshot = RegisterSnapshot(CurrentSnapshot);
+			CurrentSnapshot = RegisterSnapshotOnOwner(CurrentSnapshot,
+													  TopTransactionResourceOwner);
 			registered_serializable = true;
 		}
 
@@ -345,14 +346,27 @@ ActiveSnapshotSet(void)
 
 /*
  * RegisterSnapshot
- * 		Register a snapshot as being in use
+ * 		Register a snapshot as being in use by the current resource owner
  *
  * If InvalidSnapshot is passed, it is not registered.
  */
 Snapshot
 RegisterSnapshot(Snapshot snapshot)
 {
-	Snapshot	snap;
+	if (snapshot == InvalidSnapshot)
+		return InvalidSnapshot;
+
+	return RegisterSnapshotOnOwner(snapshot, CurrentResourceOwner);
+}
+
+/*
+ * RegisterSnapshotOnOwner
+ * 		As above, but use the specified resource owner
+ */
+Snapshot
+RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner)
+{
+	Snapshot		snap;
 
 	if (snapshot == InvalidSnapshot)
 		return InvalidSnapshot;
@@ -361,9 +375,9 @@ RegisterSnapshot(Snapshot snapshot)
 	snap = snapshot->copied ? snapshot : CopySnapshot(snapshot);
 
 	/* and tell resowner.c about it */
-	ResourceOwnerEnlargeSnapshots(CurrentResourceOwner);
+	ResourceOwnerEnlargeSnapshots(owner);
 	snap->regd_count++;
-	ResourceOwnerRememberSnapshot(CurrentResourceOwner, snap);
+	ResourceOwnerRememberSnapshot(owner, snap);
 
 	RegisteredSnapshots++;
 
@@ -383,10 +397,23 @@ UnregisterSnapshot(Snapshot snapshot)
 	if (snapshot == NULL)
 		return;
 
+	UnregisterSnapshotFromOwner(snapshot, CurrentResourceOwner);
+}
+
+/*
+ * UnregisterSnapshotFromOwner
+ * 		As above, but use the specified resource owner
+ */
+void
+UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner)
+{
+	if (snapshot == NULL)
+		return;
+
 	Assert(snapshot->regd_count > 0);
 	Assert(RegisteredSnapshots > 0);
 
-	ResourceOwnerForgetSnapshot(CurrentResourceOwner, snapshot);
+	ResourceOwnerForgetSnapshot(owner, snapshot);
 	RegisteredSnapshots--;
 	if (--snapshot->regd_count == 0 && snapshot->active_count == 0)
 	{
@@ -464,6 +491,26 @@ AtSubAbort_Snapshot(int level)
 }
 
 /*
+ * AtEarlyCommit_Snapshot
+ *
+ * Snapshot manager's cleanup function, to be called on commit, before
+ * doing resowner.c resource release.
+ */
+void
+AtEarlyCommit_Snapshot(void)
+{
+	/*
+	 * On a serializable transaction we must unregister our private refcount to
+	 * the serializable snapshot.
+	 */
+	if (registered_serializable)
+		UnregisterSnapshotFromOwner(CurrentSnapshot,
+									TopTransactionResourceOwner);
+	registered_serializable = false;
+
+}
+
+/*
  * AtEOXact_Snapshot
  * 		Snapshot manager's cleanup function for end of transaction
  */
@@ -475,13 +522,6 @@ AtEOXact_Snapshot(bool isCommit)
 	{
 		ActiveSnapshotElt	*active;
 
-		/*
-		 * On a serializable snapshot we must first unregister our private
-		 * refcount to the serializable snapshot.
-		 */
-		if (registered_serializable)
-			UnregisterSnapshot(CurrentSnapshot);
-
 		if (RegisteredSnapshots != 0)
 			elog(WARNING, "%d registered snapshots seem to remain after cleanup",
 				 RegisteredSnapshots);