Re: estimating # of distinct values - Mailing list pgsql-hackers

From Tom Lane
Subject Re: estimating # of distinct values
Date
Msg-id 25249.1295466403@sss.pgh.pa.us
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In response to Re: estimating # of distinct values  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: estimating # of distinct values  (Tomas Vondra <tv@fuzzy.cz>)
List pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> ... I guess I'm just saying I'd think really, really hard
> before abandoning the idea of periodic sampling.  You have to get an
> awful lot of benefit out of those cross-column stats to make it worth
> paying a run-time cost for them.

I've been trying to not discourage Tomas from blue-sky speculation,
but I have to say I agree with Robert that the chance of any usable
result from this approach is very very small.  Feel free to do some
experimentation to prove us wrong --- but don't put a lot of effort
into it before that.
        regards, tom lane


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