BUG #18973: The default enable_material=ON affects the cost estimation of optimizer, resulting in 10968x slow
От | PG Bug reporting form |
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Тема | BUG #18973: The default enable_material=ON affects the cost estimation of optimizer, resulting in 10968x slow |
Дата | |
Msg-id | 18973-3bc2a3f826a72cce@postgresql.org обсуждение исходный текст |
Список | pgsql-bugs |
The following bug has been logged on the website: Bug reference: 18973 Logged by: Jinhui Email address: jinhui-lai@foxmail.com PostgreSQL version: 17.5 Operating system: ubuntu 22.04 Description: Dear PG developers, Thank you for taking the time to read my report. I may have found a performance issue. The parameter enable_material is set to ON by default, and it affects the cost estimation of optimizer, resulting in 10968x slow. You can reproduce it as follows: CREATE TABLE t0(c0 INT8); CREATE TABLE t1(c1 INT8); INSERT INTO t1 SELECT i FROM generate_series(1, 100000000) AS i; SELECT * FROM t0 INNER JOIN t1 ON t0.c0 != t1.c1; c0 | c1 ----+---- (0 rows) Time: 9794.016 ms (00:09.794) SET enable_material = off; SELECT * FROM t0 INNER JOIN t1 ON t0.c0 != t1.c1; c0 | c1 ----+---- (0 rows) Time: 0.893 ms The enable_material=ON also affects CROSS/NATURAL JOIN, but not affects LEFT JOIN: SELECT * FROM t0 NATURAL JOIN t1; c0 | c1 ----+---- (0 rows) Time: 7350.216 ms (00:07.350) SELECT * FROM t0 CROSS JOIN t1; c0 | c1 ----+---- (0 rows) Time: 6823.532 ms (00:06.824) SELECT * FROM t0 LEFT JOIN t1 ON t0.c0 != t1.c1; c0 | c1 ----+---- (0 rows) Time: 0.798 ms Adding the following code in postgres/blob/master/src/backend/optimizer/util/plancat.c may works #include "catalog/pg_statistic_history.h" ... bool is_table_vacuumed_or_analyzed(Oid relid) { Relation pgstahis = NULL; SysScanDesc scan = NULL; ScanKeyData key[1]; HeapTuple tuple = NULL; bool found = false; ScanKeyInit(&key[0], Anum_pg_statistic_history_starelid, BTEqualStrategyNumber, F_OIDEQ, ObjectIdGetDatum(relid)); pgstahis = relation_open(StatisticHistoryRelationId, AccessShareLock); scan = systable_beginscan(pgstahis, StatisticHistoryTabTypAttnumIndexId, true, NULL, 1, key); if (HeapTupleIsValid(tuple = systable_getnext(scan))) { found = true; } systable_endscan(scan); relation_close(pgstahis, AccessShareLock); return found; } Best regard, Jinhui
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