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To: Alessandro Gagliardi <alessandro@path.com>
cc: pgsql-performance@postgresql.org
Subject: Re: timestamp with time zone 
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Comments: In-reply-to Alessandro Gagliardi <alessandro@path.com>
	message dated "Thu, 09 Feb 2012 10:42:15 -0800"
Date: Thu, 09 Feb 2012 14:46:06 -0500
Message-ID: <27573.1328816766@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Alessandro Gagliardi <alessandro@path.com> writes:
> WHERE ... (created at time zone timezone)::date = 'yesterday'

> created has an index (btree if it matters). timezone does not. I'm
> wondering if the solution to my problem is to create a joint index between
> created and timezone (and if so, if there is a particular way to do that to
> make it work the way I want).

The only way to make that indexable is to create an expression index on
the whole expression "(created at time zone timezone)::date".  Seems
pretty special-purpose, though it might be worthwhile if you do that a
lot.

			regards, tom lane