Fix optimization for skipping searches for parallel-query hazards.

Fix thinko in commit da1c91631: even if the original query was free of
parallel hazards, we might introduce such a hazard by adding PARAM_EXEC
Param nodes.  Adjust is_parallel_safe() so that it will scan the given
expression whenever any such nodes have been created.  Per report from
Andreas Seltenreich.

Discussion: <878tse6yvf.fsf@credativ.de>

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 1688310b8057497a282fc5429642bfa11c25a7e9..9598f28bab31f5a57b83f9180db9cbb9a7194a90 100644 (file)
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -1150,8 +1150,14 @@ is_parallel_safe(PlannerInfo *root, Node *node)
 {
        max_parallel_hazard_context context;
 
-       /* If max_parallel_hazard found nothing unsafe, we don't need to look */
-       if (root->glob->maxParallelHazard == PROPARALLEL_SAFE)
+       /*
+        * Even if the original querytree contained nothing unsafe, we need to
+        * search the expression if we have generated any PARAM_EXEC Params while
+        * planning, because those are parallel-restricted and there might be one
+        * in this expression.  But otherwise we don't need to look.
+        */
+       if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
+               root->glob->nParamExec == 0)
                return true;
        /* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
        context.max_hazard = PROPARALLEL_SAFE;