From: Tom Lane <tgl@sss.pgh.pa.us>
To: sthomas@optionshouse.com
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Possible Performance Regression with Transitive Comparisons vs. Constants
Date: Fri, 28 Sep 2012 16:35:25 -0400
Message-ID: <14848.1348864525@sss.pgh.pa.us> (raw)
In-Reply-To: <5065F910.5040504@optionshouse.com>
References: <5065F910.5040504@optionshouse.com>
Shaun Thomas <sthomas@optionshouse.com> writes:
> I ran into this while we were working on an upgrade project. We're
> moving from 8.2 (don't ask) to 9.1, and started getting terrible
> performance for some queries. I've managed to boil it down to a test case:
9.1.what? For me, 8.2.23 and 9.1.6 produce the same plan and just about
the same runtime for your query 1. For query 2, 9.1.6 prefers to stick
in a Materialize node, which cuts the runtime 30% or so --- but if I set
enable_material to off then I get the same plan and runtime as with 8.2.
Perhaps you should show the EXPLAIN ANALYZE outputs you're actually
getting, rather than assuming others will get the same thing.
regards, tom lane
(PS: it does seem that HEAD has got some kind of issue here, because
it's picking a plain not bitmap indexscan. I'll go look at that.
But I don't see that misbehavior in 9.1.)
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, sthomas@optionshouse.com
Subject: Re: Possible Performance Regression with Transitive Comparisons vs. Constants
In-Reply-To: <14848.1348864525@sss.pgh.pa.us>
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