Re: surprisingly expensive join planning query - Mailing list pgsql-hackers

From Tom Lane
Subject Re: surprisingly expensive join planning query
Date
Msg-id 18669.1575327251@sss.pgh.pa.us
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In response to Re: surprisingly expensive join planning query  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
List pgsql-hackers
Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> (Speaking of which, I don't quite see why this would have been a problem
>> once you got past geqo_threshold; the context resets that GEQO does
>> should've kept things under control.)

> Not sure I follow. geqo_threshold is 12 by default, and the OOM issues
> are hapenning way before that.

Ah, right.  But would the peak memory usage keep growing with more than 12
rels?

> It might be that one reason why this example is so bad is that the CTEs
> have *exactly* the different join orders are bound to be costed exactly
> the same I think.

Hmm.  I didn't really look into exactly why this example is so awful.

            regards, tom lane



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