From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Bad cost estimate with FALSE filter condition
Date: Mon, 16 Mar 2015 14:26:55 -0400
Message-ID: <4345.1426530415@sss.pgh.pa.us> (raw)
In-Reply-To: <55070FC9.4010307@agliodbs.com>
References: <54F119A6.9080106@agliodbs.com>
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<55070FC9.4010307@agliodbs.com>
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Josh Berkus <josh@agliodbs.com> writes:
> So ... should I assume my diagnosis is correct? Haven't heard any other
> suggestions.
I don't see any reason to think this is worth worrying about, or worth
spending planner cycles on to produce a cosmetically nicer cost estimate.
One-time filters always apply at the top plan level so they're unlikely
to change any planner choices. Moreover, for any case other than the
not-terribly-interesting constant FALSE case, we're better off assuming
that the filter condition will be true (and so there's nothing to adjust).
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, josh@agliodbs.com
Subject: Re: Bad cost estimate with FALSE filter condition
In-Reply-To: <4345.1426530415@sss.pgh.pa.us>
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