diff options
Diffstat (limited to 'src/backend/optimizer/plan/createplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/createplan.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index 9941dfe65e4..99278eed931 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -1730,8 +1730,10 @@ create_gather_plan(PlannerInfo *root, GatherPath *best_path) List *tlist; /* - * Although the Gather node can project, we prefer to push down such work - * to its child node, so demand an exact tlist from the child. + * Push projection down to the child node. That way, the projection work + * is parallelized, and there can be no system columns in the result (they + * can't travel through a tuple queue because it uses MinimalTuple + * representation). */ subplan = create_plan_recurse(root, best_path->subpath, CP_EXACT_TLIST); @@ -1766,7 +1768,7 @@ create_gather_merge_plan(PlannerInfo *root, GatherMergePath *best_path) List *pathkeys = best_path->path.pathkeys; List *tlist = build_path_tlist(root, &best_path->path); - /* As with Gather, it's best to project away columns in the workers. */ + /* As with Gather, project away columns in the workers. */ subplan = create_plan_recurse(root, best_path->subpath, CP_EXACT_TLIST); /* Create a shell for a GatherMerge plan. */ |