Обсуждение: Explain returns extremely high cost
Hi! I have a database just recreated from scratch with SQL script. (My PostgreSQL version is 8.1.3). All of the tables are pretty empty, but that's what I've got with explain: EXPLAIN SELECT * FROM account; QUERY PLAN ------------------------------------------------------------------------ Seq Scan on account (cost=100000000.00..100000001.05 rows=5 width=41) This is what I have in the table: SELECT * FROM account; obj_id | login | password | client_id | service_id | type_id | state_id ---------+---------+-------------+-----------+------------+---------+---------- 1000513 | root | _system____ | 1000471 | 1000486 | 1000113 | 1000209 1000548 | root | _system____ | 1000472 | 1000536 | 1000113 | 1000209 1000550 | root | _system____ | 1000475 | 1000534 | 1000113 | 1000209 1000552 | sol | _sol | 1000472 | 1000536 | 1000113 | 1000209 1000554 | seregik | _seregik | 1000475 | 1000534 | 1000113 | 1000209 (5 rows) Time: 1.346 ms For other tables I have more or less the same high costs. I've done VACUUM ANALYZE. This is what I have in pg_class table: SELECT relpages,reltuples FROM pg_class WHERE relname='account'; relpages | reltuples ----------+----------- 1 | 5 Why the costs are so high? Is it a bug? Thanks in advance for any suggestions! Regards, Andrii
On Tue, Aug 15, 2006 at 10:14:49AM +0300, Andrii Vasyliev wrote: > Hi! > > I have a database just recreated from scratch with SQL script. > (My PostgreSQL version is 8.1.3). > All of the tables are pretty empty, but that's what I've got with explain: > > EXPLAIN SELECT * FROM account; > QUERY PLAN > ------------------------------------------------------------------------ > Seq Scan on account (cost=100000000.00..100000001.05 rows=5 width=41) Looks like someone did an "enable_seqscan=no" somewhere, do a "show all" and check the planner variables... Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.