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From: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>
To: Michael Rothschild <michael(dot)r(at)corigin(dot)co(dot)il>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re:
Date: 2003-12-25 02:47:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
> For example, if I have the following query:
> Select * from a where x in (select y from b where z=7)
> Then I would expect an index or hash structure to be created for b.y
> when it is first scanned and brought into the cache but I couldn't see
> it happening in the source.
> As I said, I only inferred it from reading the source - not from actual
> experiments - so I may be wrong.
> 1. Am I wrong?

You are wrong - this is old behaviour and one of the major speed
improvements of PostgreSQL 7.4 is that IN subqueries now use a hash index
and hence they are much faster.


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  • at 2003-12-24 16:25:43 from Michael Rothschild

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