Re: Index usage question
От | Mitch Vincent |
---|---|
Тема | Re: Index usage question |
Дата | |
Msg-id | 00b801c13565$ca31b9b0$1e51000a@mitch обсуждение исходный текст |
Ответ на | Index usage question (Jefim Matskin <mjefim@sphera.com>) |
Список | pgsql-general |
> When I execute the explain on a simple join query I see that the indices are > NOT used for > the join: > > explain select tblAccountAvailablePlugins.nAcctPluginDirID, > tblAccountPluginDir.nAcctPluginDirID FROM tblAccountAvailablePlugins, > tblAccountPluginDir WHERE > tblAccountPluginDir.nAcctPluginDirID=tblAccountAvailablePlugins.nAcctPluginD > irID; > NOTICE: QUERY PLAN: > > Hash Join (cost=21.45..640.50 rows=6530 width=8) > -> Seq Scan on tblaccountavailableplugins (cost=0.00..187.52 rows=10452 > width=4) > -> Hash (cost=18.76..18.76 rows=1076 width=4) > -> Seq Scan on tblaccountplugindir (cost=0.00..18.76 rows=1076 > width=4) > > EXPLAIN > > can anyone explain me what is wrong with my query? If you haven't VACUUM ANALYZE 'd recently, do so to update the statistics on your table(s)... The reason it's doing a sequential scan is that a seq scan is (probably) better if that query really does return as many rows as it thinks it does.. After you update the statistics, try again and see what the query plan is then.. -Mitch
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