diff options
Diffstat (limited to 'src/backend/optimizer/plan/planmain.c')
| -rw-r--r-- | src/backend/optimizer/plan/planmain.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c index 7afd434c601..fcc0eacd253 100644 --- a/src/backend/optimizer/plan/planmain.c +++ b/src/backend/optimizer/plan/planmain.c @@ -112,14 +112,17 @@ query_planner(PlannerInfo *root, * quals are parallel-restricted. (We need not check * final_rel->reltarget because it's empty at this point. * Anything parallel-restricted in the query tlist will be - * dealt with later.) This is normally pretty silly, because - * a Result-only plan would never be interesting to - * parallelize. However, if debug_parallel_query is on, then - * we want to execute the Result in a parallel worker if - * possible, so we must do this. + * dealt with later.) We should always do this in a subquery, + * since it might be useful to use the subquery in parallel + * paths in the parent level. At top level this is normally + * not worth the cycles, because a Result-only plan would + * never be interesting to parallelize. However, if + * debug_parallel_query is on, then we want to execute the + * Result in a parallel worker if possible, so we must check. */ if (root->glob->parallelModeOK && - debug_parallel_query != DEBUG_PARALLEL_OFF) + (root->query_level > 1 || + debug_parallel_query != DEBUG_PARALLEL_OFF)) final_rel->consider_parallel = is_parallel_safe(root, parse->jointree->quals); |