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pg_plan_advice: Fix advice feedback JOIN_ORDER over a single sublist.

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Suppose that a JOIN_ORDER() advice target consists of a single
ordered or unordered sublist, something like JOIN_ORDER((...))
or JOIN_ORDER({...}) or even JOIN_ORDER(({...})).  In the previous
coding, the feedback for such advice would be "partially matched"
even when the query joined all the relations mentioned. Fix that.

Like the issues fixed by e1d8f81d49,
this escaped detection because advice generation never creates
advice strings that have the problematic form.

Reported-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Discussion: http://postgr.es/m/CAJTYsWWe8E8ya-24wRws5LSVhHNxCwLyy8c-ueY-TKvC=8P7UQ@mail.gmail.com
Discussion: http://postgr.es/m/CA+TgmoYYHC4i-Gpzc9-JYHqih6pOK+6LTYFiNR-PioXG1nKkOQ@mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Robert Haas
2026-10-09 13:57:08 -04:00
parent f71a9969d5
commit f6065c56d4
3 changed files with 95 additions and 1 deletions
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59
contrib/pg_plan_advice/expected/join_order.out
View File

@@ -249,6 +249,65 @@ SELECT * FROM jo_fact f
NO_GATHER(f d1 d2)
(18 rows)
COMMIT;
-- Test cases for sublists spanning all targets.
BEGIN;
SET LOCAL pg_plan_advice.advice = 'join_order((f d1 d2))';
EXPLAIN (COSTS OFF, PLAN_ADVICE)
SELECT * FROM jo_fact f
LEFT JOIN jo_dim1 d1 ON f.dim1_id = d1.id
LEFT JOIN jo_dim2 d2 ON f.dim2_id = d2.id
WHERE val1 = 1 AND val2 = 1;
QUERY PLAN
------------------------------------------
Hash Join
Hash Cond: (f.dim2_id = d2.id)
-> Hash Join
Hash Cond: (f.dim1_id = d1.id)
-> Seq Scan on jo_fact f
-> Hash
-> Seq Scan on jo_dim1 d1
Filter: (val1 = 1)
-> Hash
-> Seq Scan on jo_dim2 d2
Filter: (val2 = 1)
Supplied Plan Advice:
JOIN_ORDER((f d1 d2)) /* matched */
Generated Plan Advice:
JOIN_ORDER(f d1 d2)
HASH_JOIN(d1 d2)
SEQ_SCAN(f d1 d2)
NO_GATHER(f d1 d2)
(18 rows)
SET LOCAL pg_plan_advice.advice = 'join_order({f d1 d2})';
EXPLAIN (COSTS OFF, PLAN_ADVICE)
SELECT * FROM jo_fact f
LEFT JOIN jo_dim1 d1 ON f.dim1_id = d1.id
LEFT JOIN jo_dim2 d2 ON f.dim2_id = d2.id
WHERE val1 = 1 AND val2 = 1;
QUERY PLAN
------------------------------------------
Hash Join
Hash Cond: (f.dim1_id = d1.id)
-> Hash Join
Hash Cond: (f.dim2_id = d2.id)
-> Seq Scan on jo_fact f
-> Hash
-> Seq Scan on jo_dim2 d2
Filter: (val2 = 1)
-> Hash
-> Seq Scan on jo_dim1 d1
Filter: (val1 = 1)
Supplied Plan Advice:
JOIN_ORDER({f d1 d2}) /* matched */
Generated Plan Advice:
JOIN_ORDER(f d2 d1)
HASH_JOIN(d2 d1)
SEQ_SCAN(f d2 d1)
NO_GATHER(f d1 d2)
(18 rows)
COMMIT;
-- Test cases for single-element groupings. The extra grouping levels should
-- be ignored.

21
contrib/pg_plan_advice/pgpa_planner.c
View File

@@ -1241,14 +1241,33 @@ pgpa_join_order_permits_join(int outer_count, int inner_count,
{
if (child_target->ttype == PGPA_TARGET_ORDERED_LIST)
{
/*
* JOIN_ORDER((...)) is treated as syntactic sugar; the
* extra level of parentheses does not change the
* interpretation. Hence, don't set sublist = true in that
* case.
*/
if (list_length(target->children) != 1)
sublist = true;
target = child_target;
sublist = true;
loop = true;
break;
}
else
{
Assert(child_target->ttype == PGPA_TARGET_UNORDERED_LIST);
/*
* If an unordered sublist is the entire advice target,
* for example because the user writes JOIN_ORDER({...})
* or JOIN_ORDER(({...})), and if the join we're
* considering contains exactly the mentioned relations,
* we need to mark this advice as fully matched, because
* that won't happen anywhere else.
*/
if (itm == PGPA_ITM_EQUAL && !sublist &&
list_length(target->children) == 1)
entry->flags |= PGPA_FB_MATCH_FULL;
return PGPA_JO_INDIFFERENT;
}
}

16
contrib/pg_plan_advice/sql/join_order.sql
View File

@@ -82,6 +82,22 @@ SELECT * FROM jo_fact f
WHERE val1 = 1 AND val2 = 1;
COMMIT;
-- Test cases for sublists spanning all targets.
BEGIN;
SET LOCAL pg_plan_advice.advice = 'join_order((f d1 d2))';
EXPLAIN (COSTS OFF, PLAN_ADVICE)
SELECT * FROM jo_fact f
LEFT JOIN jo_dim1 d1 ON f.dim1_id = d1.id
LEFT JOIN jo_dim2 d2 ON f.dim2_id = d2.id
WHERE val1 = 1 AND val2 = 1;
SET LOCAL pg_plan_advice.advice = 'join_order({f d1 d2})';
EXPLAIN (COSTS OFF, PLAN_ADVICE)
SELECT * FROM jo_fact f
LEFT JOIN jo_dim1 d1 ON f.dim1_id = d1.id
LEFT JOIN jo_dim2 d2 ON f.dim2_id = d2.id
WHERE val1 = 1 AND val2 = 1;
COMMIT;
-- Test cases for single-element groupings. The extra grouping levels should
-- be ignored.
BEGIN;