1 files changed, 56 insertions, 0 deletions

diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index 66e31818156..5c30e141f52 100644
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -502,6 +502,9 @@ PortalDrop(Portal portal, bool isTopCommit)
 		portal->cleanup = NULL;
 	}
 
+	/* There shouldn't be an active snapshot anymore, except after error */
+	Assert(portal->portalSnapshot == NULL || !isTopCommit);
+
 	/*
 	 * Remove portal from hash table.  Because we do this here, we will not
 	 * come back to try to remove the portal again if there's any error in the
@@ -709,6 +712,8 @@ PreCommit_Portals(bool isPrepare)
 				portal->holdSnapshot = NULL;
 			}
 			portal->resowner = NULL;
+			/* Clear portalSnapshot too, for cleanliness */
+			portal->portalSnapshot = NULL;
 			continue;
 		}
 
@@ -1278,3 +1283,54 @@ HoldPinnedPortals(void)
 		}
 	}
 }
+
+/*
+ * Drop the outer active snapshots for all portals, so that no snapshots
+ * remain active.
+ *
+ * Like HoldPinnedPortals, this must be called when initiating a COMMIT or
+ * ROLLBACK inside a procedure.  This has to be separate from that since it
+ * should not be run until we're done with steps that are likely to fail.
+ *
+ * It's tempting to fold this into PreCommit_Portals, but to do so, we'd
+ * need to clean up snapshot management in VACUUM and perhaps other places.
+ */
+void
+ForgetPortalSnapshots(void)
+{
+	HASH_SEQ_STATUS status;
+	PortalHashEnt *hentry;
+	int			numPortalSnaps = 0;
+	int			numActiveSnaps = 0;
+
+	/* First, scan PortalHashTable and clear portalSnapshot fields */
+	hash_seq_init(&status, PortalHashTable);
+
+	while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
+	{
+		Portal		portal = hentry->portal;
+
+		if (portal->portalSnapshot != NULL)
+		{
+			portal->portalSnapshot = NULL;
+			numPortalSnaps++;
+		}
+		/* portal->holdSnapshot will be cleaned up in PreCommit_Portals */
+	}
+
+	/*
+	 * Now, pop all the active snapshots, which should be just those that were
+	 * portal snapshots.  Ideally we'd drive this directly off the portal
+	 * scan, but there's no good way to visit the portals in the correct
+	 * order.  So just cross-check after the fact.
+	 */
+	while (ActiveSnapshotSet())
+	{
+		PopActiveSnapshot();
+		numActiveSnaps++;
+	}
+
+	if (numPortalSnaps != numActiveSnaps)
+		elog(ERROR, "portal snapshots (%d) did not account for all active snapshots (%d)",
+			 numPortalSnaps, numActiveSnaps);
+}