Re: Query with large number of joins - Mailing list pgsql-performance

From Tom Lane
Subject Re: Query with large number of joins
Date
Msg-id 6038.1413910006@sss.pgh.pa.us
Whole thread Raw
In response to Re: Query with large number of joins  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: Query with large number of joins  (Marco Di Cesare <Marco.DiCesare@pointclickcare.com>)
List pgsql-performance
Andrew Dunstan <andrew@dunslane.net> writes:
> Have you tried a) either turning off geqo or setting geqo_threshold
> fairly high b) setting join_collapse_limit fairly high (assuming all the
> above join targets are tables and not views, setting it to something
> like 25 should do the trick.

You'd have to do both, I think, to get an exhaustive plan search.

In any case, this query is going to result in full table scans of most
of the tables, because there just aren't very many WHERE constraints;
so expecting it to run instantaneously is a pipe dream.  I'm not sure
that there's a significantly better plan to be had.

            regards, tom lane


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