diff options
| -rw-r--r-- | src/backend/optimizer/prep/prepjointree.c | 19 | ||||
| -rw-r--r-- | src/test/regress/expected/join.out | 31 | ||||
| -rw-r--r-- | src/test/regress/sql/join.sql | 8 |
3 files changed, 51 insertions, 7 deletions
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c index 2f589b1b99f..73ff40721c9 100644 --- a/src/backend/optimizer/prep/prepjointree.c +++ b/src/backend/optimizer/prep/prepjointree.c @@ -3213,6 +3213,8 @@ remove_useless_result_rtes(PlannerInfo *root) * jtnode is the current jointree node. If it could be valid to merge * its quals into those of the parent node, parent_quals should point to * the parent's quals list; otherwise, pass NULL for parent_quals. + * (Note that in some cases, parent_quals points to the quals of a parent + * more than one level up in the tree.) */ static Node * remove_useless_results_recurse(PlannerInfo *root, Node *jtnode, @@ -3316,13 +3318,22 @@ remove_useless_results_recurse(PlannerInfo *root, Node *jtnode, int varno; /* - * First, recurse. We can accept pushed-up FromExpr quals from either - * child if the jointype is INNER, and we can accept them from the RHS - * child if the jointype is LEFT. + * First, recurse. We can absorb pushed-up FromExpr quals from either + * child into this node if the jointype is INNER, since then this is + * equivalent to a FromExpr. When the jointype is LEFT, we can absorb + * quals from the RHS child into the current node, as they're + * essentially degenerate quals of the outer join. Moreover, if we've + * been passed down a parent_quals pointer then we can allow quals of + * the LHS child to be absorbed into the parent. (This is important + * to ensure we remove single-child FromExprs immediately below + * commutable left joins.) For other jointypes, we can't move child + * quals up, or at least there's no particular reason to. */ j->larg = remove_useless_results_recurse(root, j->larg, (j->jointype == JOIN_INNER) ? - &j->quals : NULL, + &j->quals : + (j->jointype == JOIN_LEFT) ? + parent_quals : NULL, dropped_outer_joins); j->rarg = remove_useless_results_recurse(root, j->rarg, (j->jointype == JOIN_INNER || diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out index cd1163d039b..6917faec141 100644 --- a/src/test/regress/expected/join.out +++ b/src/test/regress/expected/join.out @@ -2531,20 +2531,45 @@ select * from int4_tbl t1 on s.f1 = t1.f1; QUERY PLAN ------------------------------------------------- + Hash Right Join + Hash Cond: (t2.f1 = t1.f1) + -> Nested Loop Left Join + Join Filter: (t2.f1 > 1) + -> Nested Loop Left Join + Join Filter: (t2.f1 > 0) + Filter: (t3.f1 IS NULL) + -> Seq Scan on int4_tbl t2 + -> Materialize + -> Seq Scan on int4_tbl t3 + -> Seq Scan on tenk1 t4 + -> Hash + -> Seq Scan on int4_tbl t1 +(13 rows) + +explain (costs off) +select * from int4_tbl t1 + left join ((select t2.f1 from int4_tbl t2 + left join int4_tbl t3 on t2.f1 > 0 + where t2.f1 <> coalesce(t3.f1, -1)) s + left join tenk1 t4 on s.f1 > 1) + on s.f1 = t1.f1; + QUERY PLAN +----------------------------------------------------------------- Nested Loop Left Join Join Filter: (t2.f1 > 1) -> Hash Right Join Hash Cond: (t2.f1 = t1.f1) -> Nested Loop Left Join Join Filter: (t2.f1 > 0) - Filter: (t3.f1 IS NULL) + Filter: (t2.f1 <> COALESCE(t3.f1, '-1'::integer)) -> Seq Scan on int4_tbl t2 -> Materialize -> Seq Scan on int4_tbl t3 -> Hash -> Seq Scan on int4_tbl t1 - -> Seq Scan on tenk1 t4 -(13 rows) + -> Materialize + -> Seq Scan on tenk1 t4 +(14 rows) explain (costs off) select * from onek t1 diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql index 7ca737eec0f..55080bec9af 100644 --- a/src/test/regress/sql/join.sql +++ b/src/test/regress/sql/join.sql @@ -503,6 +503,14 @@ select * from int4_tbl t1 on s.f1 = t1.f1; explain (costs off) +select * from int4_tbl t1 + left join ((select t2.f1 from int4_tbl t2 + left join int4_tbl t3 on t2.f1 > 0 + where t2.f1 <> coalesce(t3.f1, -1)) s + left join tenk1 t4 on s.f1 > 1) + on s.f1 = t1.f1; + +explain (costs off) select * from onek t1 left join onek t2 on t1.unique1 = t2.unique1 left join onek t3 on t2.unique1 = t3.unique1 |