diff options
Diffstat (limited to 'src/backend/optimizer/path/joinpath.c')
| -rw-r--r-- | src/backend/optimizer/path/joinpath.c | 36 |
1 files changed, 32 insertions, 4 deletions
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index 02a630278f7..e774130ac8d 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -747,7 +747,7 @@ try_hashjoin_path(PlannerInfo *root, * never have any output pathkeys, per comments in create_hashjoin_path. */ initial_cost_hashjoin(root, &workspace, jointype, hashclauses, - outer_path, inner_path, extra); + outer_path, inner_path, extra, false); if (add_path_precheck(joinrel, workspace.startup_cost, workspace.total_cost, @@ -761,6 +761,7 @@ try_hashjoin_path(PlannerInfo *root, extra, outer_path, inner_path, + false, /* parallel_hash */ extra->restrictlist, required_outer, hashclauses)); @@ -776,6 +777,10 @@ try_hashjoin_path(PlannerInfo *root, * try_partial_hashjoin_path * Consider a partial hashjoin join path; if it appears useful, push it into * the joinrel's partial_pathlist via add_partial_path(). + * The outer side is partial. If parallel_hash is true, then the inner path + * must be partial and will be run in parallel to create one or more shared + * hash tables; otherwise the inner path must be complete and a copy of it + * is run in every process to create separate identical private hash tables. */ static void try_partial_hashjoin_path(PlannerInfo *root, @@ -784,7 +789,8 @@ try_partial_hashjoin_path(PlannerInfo *root, Path *inner_path, List *hashclauses, JoinType jointype, - JoinPathExtraData *extra) + JoinPathExtraData *extra, + bool parallel_hash) { JoinCostWorkspace workspace; @@ -808,7 +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); + outer_path, inner_path, extra, true); if (!add_partial_path_precheck(joinrel, workspace.total_cost, NIL)) return; @@ -821,6 +827,7 @@ try_partial_hashjoin_path(PlannerInfo *root, extra, outer_path, inner_path, + parallel_hash, extra->restrictlist, NULL, hashclauses)); @@ -1839,6 +1846,10 @@ hash_inner_and_outer(PlannerInfo *root, * able to properly guarantee uniqueness. Similarly, we can't handle * JOIN_FULL and JOIN_RIGHT, because they can produce false null * extended rows. Also, the resulting path must not be parameterized. + * We would be able to support JOIN_FULL and JOIN_RIGHT for Parallel + * Hash, since in that case we're back to a single hash table with a + * single set of match bits for each batch, but that will require + * figuring out a deadlock-free way to wait for the probe to finish. */ if (joinrel->consider_parallel && save_jointype != JOIN_UNIQUE_OUTER && @@ -1848,12 +1859,28 @@ hash_inner_and_outer(PlannerInfo *root, bms_is_empty(joinrel->lateral_relids)) { Path *cheapest_partial_outer; + Path *cheapest_partial_inner = NULL; Path *cheapest_safe_inner = NULL; cheapest_partial_outer = (Path *) linitial(outerrel->partial_pathlist); /* + * Can we use a partial inner plan too, so that we can build a + * shared hash table in parallel? + */ + if (innerrel->partial_pathlist != NIL && enable_parallel_hash) + { + cheapest_partial_inner = + (Path *) linitial(innerrel->partial_pathlist); + try_partial_hashjoin_path(root, joinrel, + cheapest_partial_outer, + cheapest_partial_inner, + hashclauses, jointype, extra, + true /* parallel_hash */ ); + } + + /* * Normally, given that the joinrel is parallel-safe, the cheapest * total inner path will also be parallel-safe, but if not, we'll * have to search for the cheapest safe, unparameterized inner @@ -1870,7 +1897,8 @@ hash_inner_and_outer(PlannerInfo *root, try_partial_hashjoin_path(root, joinrel, cheapest_partial_outer, cheapest_safe_inner, - hashclauses, jointype, extra); + hashclauses, jointype, extra, + false /* parallel_hash */ ); } } } |