Re: How to uses self query plan
От | olivier.boissard@cerene.fr |
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Тема | Re: How to uses self query plan |
Дата | |
Msg-id | 476999FC.9090306@cerene.fr обсуждение исходный текст |
Ответ на | Re: How to uses self query plan ("Scott Marlowe" <scott.marlowe@gmail.com>) |
Ответы |
Re: How to uses self query plan
(Guillaume Lelarge <guillaume@lelarge.info>)
Re: How to uses self query plan ("Scott Marlowe" <scott.marlowe@gmail.com>) |
Список | pgsql-admin |
You're right . I will begin by migrate postgresql version. postgresql is now to 8.3 version . A lot of performance inprovements have been made in this last version . In any case I must do a pg_dump/pg_restore. So , Should I try directly 8.3 version or is it more cautious to stay in 8.1.x version ? Olivier Scott Marlowe a écrit : > On Dec 19, 2007 1:57 AM, olivier boissard <olivier.boissard@cerene.fr> wrote: > >> Scott Marlowe a écrit : >> >> >>> On Dec 18, 2007 4:21 PM, olivier.boissard@cerene.fr >>> <olivier.boissard@cerene.fr> wrote: >>> >>> >>>> Hello, >>>> >>>> My purpose is to uses different query plan depending on queries >>>> I got the following problem : some queries are taking too much time and >>>> postgresql does not take the most relevant index in account. >>>> I search on internet and found that no HINT function was available in >>>> postgresl. >>>> I tried to change indexes parameters in postgresql.conf but eache time I >>>> set a param to OFF (example nested_loop ,seqscan, ...) , some queries >>>> freeze database . >>>> >>>> How can we force postgresql to use a plan ? >>>> >>>> >>> That's not how we do things in postgresql land (usually). >>> >>> You should figure out WHY your queries are picking the wrong plan, and >>> then see if you can get them to pick the right ones. If it's a query >>> planner bug, you report it here, or the perform or general lists, and >>> it gets fixed. Generic hints aren't likely to happen any time soon, >>> although I do believe 8.3 is introducing function costing of some >>> kind, which seems like a useful idea. >>> >>> But, back to fixing your slow queries. >>> >>> 1: Increase statistics targets on the guilty columns and reanalyze. >>> 2: Run explain analyze select.... and post the output here. >>> 3: ??? >>> 4: profit? >>> >>> >> Thanks for reply >> >> I will extract some queries. >> I want to precise that I use postgresql 8.1.0 . >> > > First step would be to update to the latest 8.1.x version, whatever > that is. There have been a LOT of fixes in the 8.1 branch since 8.1.0 > came out, and one might be a fix for your query problem. minor > updates are strictly bug and security fixes, so they're not likely to > cause any problems. > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > >
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