2 files changed, 20 insertions, 1 deletions
diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index a34abbd80c4..11ee752f84a 100644
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -210,6 +210,7 @@ CreatePortal(const char *name, bool allowDup, bool dupSilent)
 	portal->cleanup = PortalCleanup;
 	portal->createSubid = GetCurrentSubTransactionId();
 	portal->activeSubid = portal->createSubid;
+	portal->createLevel = GetCurrentTransactionNestLevel();
 	portal->strategy = PORTAL_MULTI_QUERY;
 	portal->cursorOptions = CURSOR_OPT_NO_SCROLL;
 	portal->atStart = true;
@@ -657,6 +658,7 @@ HoldPortal(Portal portal)
 	 */
 	portal->createSubid = InvalidSubTransactionId;
 	portal->activeSubid = InvalidSubTransactionId;
+	portal->createLevel = 0;
 }
 
 /*
@@ -940,6 +942,7 @@ PortalErrorCleanup(void)
 void
 AtSubCommit_Portals(SubTransactionId mySubid,
 					SubTransactionId parentSubid,
+					int parentLevel,
 					ResourceOwner parentXactOwner)
 {
 	HASH_SEQ_STATUS status;
@@ -954,6 +957,7 @@ AtSubCommit_Portals(SubTransactionId mySubid,
 		if (portal->createSubid == mySubid)
 		{
 			portal->createSubid = parentSubid;
+			portal->createLevel = parentLevel;
 			if (portal->resowner)
 				ResourceOwnerNewParent(portal->resowner, parentXactOwner);
 		}
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
index 5e3b31ba902..1c960300fd2 100644
--- a/src/backend/utils/time/snapmgr.c
+++ b/src/backend/utils/time/snapmgr.c
@@ -734,9 +734,24 @@ FreeSnapshot(Snapshot snapshot)
 void
 PushActiveSnapshot(Snapshot snap)
 {
+	PushActiveSnapshotWithLevel(snap, GetCurrentTransactionNestLevel());
+}
+
+/*
+ * PushActiveSnapshotWithLevel
+ *		Set the given snapshot as the current active snapshot
+ *
+ * Same as PushActiveSnapshot except that caller can specify the
+ * transaction nesting level that "owns" the snapshot.  This level
+ * must not be deeper than the current top of the snapshot stack.
+ */
+void
+PushActiveSnapshotWithLevel(Snapshot snap, int snap_level)
+{
 	ActiveSnapshotElt *newactive;
 
 	Assert(snap != InvalidSnapshot);
+	Assert(ActiveSnapshot == NULL || snap_level >= ActiveSnapshot->as_level);
 
 	newactive = MemoryContextAlloc(TopTransactionContext, sizeof(ActiveSnapshotElt));
 
@@ -750,7 +765,7 @@ PushActiveSnapshot(Snapshot snap)
 		newactive->as_snap = snap;
 
 	newactive->as_next = ActiveSnapshot;
-	newactive->as_level = GetCurrentTransactionNestLevel();
+	newactive->as_level = snap_level;
 
 	newactive->as_snap->active_count++;