Basic question about indexes (6.5.2)
От | Alain TESIO |
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Тема | Basic question about indexes (6.5.2) |
Дата | |
Msg-id | 008501bf2fc8$323ebbc0$f65f72c3@atesio обсуждение исходный текст |
Ответ на | Re: [GENERAL] [ADMIN] 6.5.3/doesn't recognize localhost in pg_hba.conf (fwd) (Larry Rosenman <ler@lerami.lerctr.org>) |
Ответы |
Re: [GENERAL] Basic question about indexes (6.5.2)
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Список | pgsql-general |
create table T1 ( x int ); create table T2 ( y int ); < insert from 1 to 1000 in T1 and T2> create index idx_t1 on T1 ( x ); create index idx_t2 on T2 ( y ); explain select T1.x from T1,T2 where T1.x=T2.y; drop table T1; drop table T2; Hash Join (cost=155.00 rows=1001 width=8) -> Seq Scan on t2 (cost=43.00 rows=1000 width=4) -> Hash (cost=43.00 rows=1000 width=4) -> Seq Scan on t1 (cost=43.00 rows=1000 width=4) I'm surprised that this simple query can't use indexes, or it does and it's not reported in the explain output ? By the way, with these tables, why does this query return 1000 and not 1000000 ? select count(*) from T1,T2; count ----- 1000 (1 row) Alain
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