Re: [PERFORM] Bad n_distinct estimation; hacks suggested? - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [PERFORM] Bad n_distinct estimation; hacks suggested?
Date
Msg-id 10257.1114405167@sss.pgh.pa.us
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In response to Re: [PERFORM] Bad n_distinct estimation; hacks suggested?  (Josh Berkus <josh@agliodbs.com>)
List pgsql-hackers
Josh Berkus <josh@agliodbs.com> writes:
> Tom, how does our heuristic sampling work?   Is it pure random sampling, or
> page sampling?

Manfred probably remembers better than I do, but I think the idea is
to approximate pure random sampling as best we can without actually
examining every page of the table.

            regards, tom lane

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