From d817d719c63c014f28376251012f56275e100d18 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 22 Dec 2017 23:58:15 +1300 Subject: [PATCH] Fix costing of parallel hash joins. Commit 1804284042e659e7d16904e7bbb0ad546394b6a3 established that single-batch parallel-aware hash joins could create one large shared hash table using the combined work_mem budget of all participants. The costing accidentally assumed that parallel-oblivious hash joins could also do that. The documentation for initial_cost_hashjoin() also failed to mention the new argument. Repair. Author: Thomas Munro Reported-By: Antonin Houska Reviewed-By: Antonin Houska Discussion: https://postgr.es/m/12441.1513935950%40localhost --- src/backend/optimizer/path/costsize.c | 2 ++ src/backend/optimizer/path/joinpath.c | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index d8db0b29e1..36b3dfabb8 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -3143,6 +3143,8 @@ cached_scansel(PlannerInfo *root, RestrictInfo *rinfo, PathKey *pathkey) * 'outer_path' is the outer input to the join * 'inner_path' is the inner input to the join * 'extra' contains miscellaneous information about the join + * 'parallel_hash' indicates that inner_path is partial and that a shared + * hash table will be built in parallel */ void initial_cost_hashjoin(PlannerInfo *root, JoinCostWorkspace *workspace, diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index 688f440b92..3fd3cc7670 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -814,7 +814,7 @@ try_partial_hashjoin_path(PlannerInfo *root, * cost. Bail out right away if it looks terrible. */ initial_cost_hashjoin(root, &workspace, jointype, hashclauses, - outer_path, inner_path, extra, true); + outer_path, inner_path, extra, parallel_hash); if (!add_partial_path_precheck(joinrel, workspace.total_cost, NIL)) return; -- 2.15.1