Re: Bad cost estimate with FALSE filter condition - Mailing list pgsql-performance

From Tom Lane
Subject Re: Bad cost estimate with FALSE filter condition
Date
Msg-id 4345.1426530415@sss.pgh.pa.us
Whole thread Raw
In response to Re: Bad cost estimate with FALSE filter condition  (Josh Berkus <josh@agliodbs.com>)
List pgsql-performance
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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