Re: Optimizer : query rewrite and execution plan ?

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От Richard Huxton
Тема Re: Optimizer : query rewrite and execution plan ?
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Msg-id 47A986B7.3000809@archonet.com
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Ответ на Re: Optimizer : query rewrite and execution plan ?  (SURANTYN Jean François <jfsurant@supermarchesmatch.fr>)
Список pgsql-performance
SURANTYN Jean François wrote:
> Many thanks for your quick reply
>
> In fact, that issue comes from a recent migration from Oracle to
> Postgresql, and even if some queries were not optimized by the past
> (example: where n=1 and n=1), Oracle was able to rewrite them and to
> "hide" the bad queries". But now that we have migrated to Postgresql,
> we have discovered that some queries were indeed badly wroten I will
> tell to the developpers to try to optimize their queries for them to
> work efficiently on Postgresql

If nothing else it will help when / if you decide to use prepared
queries - there's no way to optimise "n=$1 or n=$2" at planning time.

--
  Richard Huxton
  Archonet Ltd

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