Re: Improving N-Distinct estimation by ANALYZE

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Improving N-Distinct estimation by ANALYZE
Date: 2006-01-16 20:38:23
Message-ID: 17803.1137443903@sss.pgh.pa.us
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Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Tom has not spoken against checking for UNIQUE constraints: he is just
> pointing out that there never could be a constraint in the case I was
> identifying.

More generally, arguing for or against any system-wide change on the
basis of performance of compute_minimal_stats() is folly, because that
function is not used for any common datatypes. (Ideally it'd never be
used at all.)

regards, tom lane

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