There's a small window wherein a transaction is committed but not yet

on the finished list, and we shouldn't flag it as a potential conflict
if so. We can also skip adding a doomed transaction to the list of
possible conflicts because we know it won't commit.

Dan Ports and Kevin Grittner.

src/backend/storage/lmgr/predicate.c

@@ -1677,8 +1677,9 @@ RegisterSerializableTransactionInt(Snapshot snapshot)
 			 othersxact != NULL;
 			 othersxact = NextPredXact(othersxact))
 		{
-			if (!SxactIsOnFinishedList(othersxact) &&
-				!SxactIsReadOnly(othersxact))
+			if (!SxactIsCommitted(othersxact)
+				&& !SxactIsDoomed(othersxact)
+				&& !SxactIsReadOnly(othersxact))
 			{
 				SetPossibleUnsafeConflict(sxact, othersxact);
 			}