Re: Proposal - improve eqsel estimates by including histogram bucket numdistinct statistics - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Proposal - improve eqsel estimates by including histogram bucket numdistinct statistics
Date
Msg-id 22404.1213124051@sss.pgh.pa.us
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In response to Re: Proposal - improve eqsel estimates by including histogram bucket numdistinct statistics  ("Nathan Boley" <npboley@gmail.com>)
Responses Re: Proposal - improve eqsel estimates by including histogram bucket numdistinct statistics
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"Nathan Boley" <npboley@gmail.com> writes:
> If we query on values that aren't in the table, the planner will
> always overestimate the expected number of returned rows because it (
> implicitly ) assumes that every query will return at least 1 record.

That's intentional and should not be changed.  I can't see the value
of allowing fractional-row estimates anyway.  Now if we can *prove*
the query matches no rows, that's a whole nother matter, but statistics
won't help us with that.
        regards, tom lane


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