Fix active snapshot checks

Author: pashkinelfe

src/backend/executor/execMain.c

@@ -150,7 +150,7 @@ standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
 	Assert(queryDesc->estate == NULL);
 
 	/* caller must ensure the query's snapshot is active */
-	Assert(GetActiveSnapshot() == queryDesc->snapshot);
+	Assert((ActiveSnapshotSet() ? GetActiveSnapshot() : InvalidSnapshot) == queryDesc->snapshot);
 
 	/*
 	 * If the transaction is read-only, we need to check if any writes are
@@ -325,7 +325,7 @@ standard_ExecutorRun(QueryDesc *queryDesc,
 	Assert(!(estate->es_top_eflags & EXEC_FLAG_EXPLAIN_ONLY));
 
 	/* caller must ensure the query's snapshot is active */
-	Assert(GetActiveSnapshot() == estate->es_snapshot);
+	Assert((ActiveSnapshotSet() ? GetActiveSnapshot() : InvalidSnapshot) == estate->es_snapshot);
 
 	/*
 	 * Switch into per-query memory context