[EXPLAIN] Nested loops
| От | Reg Me Please |
|---|---|
| Тема | [EXPLAIN] Nested loops |
| Дата | |
| Msg-id | 200901091906.27568.regmeplease@gmail.com обсуждение исходный текст |
| Ответы |
Re: [EXPLAIN] Nested loops
|
| Список | pgsql-general |
Hi. For an INNER JOINed query, EXPLAIN says that a "nested loop" is responsible for the big part of the time needed to run. The 2 tables JOINed are: T1: multi-million rows T2: few dozens rows The join is though a single column in both sides and it's NOT a PK in either table. But I have indexes in both T1 and T2 for that column. I've read in the "Explaining EXPLAIN" by Rober Treat (at http://wiki.postgresql.org/wiki/Image:OSCON2005-ExplainingExplain.sxi) that this nested loop can be slow because of lacking of indexes. Is there any hint to try to speed that query up? As of now, only a REINDEX can help thanks to caching, I presume. But the EXPLAIN still says there's a slow nested loop. -- Fahrbahn ist ein graues Band weisse Streifen, grüner Rand
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