Re: [PERFORM] strange and slow joining of nested views

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От Tom Lane
Тема Re: [PERFORM] strange and slow joining of nested views
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Msg-id 20264.1486185381@sss.pgh.pa.us
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Ответ на [PERFORM] strange and slow joining of nested views  (Titus von Boxberg <titus@elbe-informatik.de>)
Ответы Re: [PERFORM] strange and slow joining of nested views  (Titus von Boxberg <titus@elbe-informatik.de>)
Список pgsql-performance
Titus von Boxberg <titus@elbe-informatik.de> writes:
> I got the following problem for which I could not find a solution by searching the archives:
> I have Tables Ta, Tb, Tc with primary keys as bigserials.
> Ta references Tb references Tc.
> Not all but most rows in Ta reference exactly one row in Tb.

Hm, your problem query has 11 table scans (not to mention a couple of
subplans) so you're oversimplifying here.  Anyway, I think that increasing
join_collapse_limit and/or from_collapse_limit to at least 11 might help.
As-is, you're more or less at the mercy of whether your textual query
structure corresponds to a good join order.

            regards, tom lane


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