Re: How to read a query plan?
От | Peter Eisentraut |
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Тема | Re: How to read a query plan? |
Дата | |
Msg-id | Pine.LNX.4.30.0104181731200.762-100000@peter.localdomain обсуждение исходный текст |
Ответ на | How to read a query plan? (elwood@agouros.de (Konstantinos Agouros)) |
Ответы |
Re: How to read a query plan?
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Список | pgsql-general |
Konstantinos Agouros writes: > logs=> explain select distinct on (url) url, category, action from websenseflat where webhost='dir.yahoo.com' and datum>='1-26-2001' and datum < '1-27-2001'; > NOTICE: QUERY PLAN: > > Unique (cost=0.01..0.01 rows=1 width=36) > -> Sort (cost=0.01..0.01 rows=1 width=36) > -> Seq Scan on websenseflat (cost=0.00..0.00 rows=1 width=36) > > EXPLAIN > > after this I created an index on the field webhost, now the query plan says: > > NOTICE: QUERY PLAN: > > Unique (cost=19690.08..19690.22 rows=5 width=36) > -> Sort (cost=19690.08..19690.08 rows=53 width=36) > -> Index Scan using wsflwebhost on websenseflat (cost=0.00..19688.55 rows=53 width=36) > > EXPLAIN > > Could someone give me an interpretation (or a URL that explains this)? http://www.de.postgresql.org/devel-corner/docs/postgres/performance-tips.html -- Peter Eisentraut peter_e@gmx.net http://funkturm.homeip.net/~peter
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