Re: Opptimizing projections containing unused columns - Mailing list pgsql-general

From Tom Lane
Subject Re: Opptimizing projections containing unused columns
Date
Msg-id 24244.1224092193@sss.pgh.pa.us
Whole thread Raw
In response to Re: Opptimizing projections containing unused columns  ("Andrus" <kobruleht2@hot.ee>)
Responses Re: Optimizing projections containing unused columns  ("Andrus" <kobruleht2@hot.ee>)
List pgsql-general
"Andrus" <kobruleht2@hot.ee> writes:
> Is it OK to put all filters to outer query WHERE clase?
> Or should I move as many filter conditions as possible to inner query so
> that inner query returns 10000 records instead of 500000 records.

> Is there difference in perfomance if inner query returs large number of rows
> which are filtered only by outer query ?

This question is too vague to be answerable --- especially if you want
an answer that applies across all 8.x releases.  I'd suggest
experimenting a bit using EXPLAIN ANALYZE to see what happens in your
actual application.

            regards, tom lane

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