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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <peter@2ndquadrant.com>
Cc: Thom Brown <thom@linux.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Unused index influencing sequential scan plan
Date: Thu, 18 Oct 2012 13:06:32 -0400
Message-ID: <603.1350579992@sss.pgh.pa.us> (raw)
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Peter Geoghegan <peter@2ndquadrant.com> writes:
> Is there a case to be made for a index access method whose
> pseudo-indexes costs essentially nothing to maintain, and simply
> represent an ongoing obligation for ANALYZE to provide statistics for
> an expression?

If we were going to support it, I think we'd be better off exposing such
a feature as DDL having nothing to do with indexes.  Not sure it's worth
the trouble though.  The ANALYZE wart to compute stats for index
expressions has been there a long time, and there's been essentially
zero field demand for another way to do it.  What people really seem to
care about is more intelligence about making use of expression indexes
to avoid recalculation of the expression --- something you'd not get
from a stats-only feature.

			regards, tom lane

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