Re: Aggregate and many LEFT JOIN - Mailing list pgsql-performance

From Tom Lane
Subject Re: Aggregate and many LEFT JOIN
Date
Msg-id 17803.1550858759@sss.pgh.pa.us
Whole thread Raw
In response to Re: Aggregate and many LEFT JOIN  (Michael Lewis <mlewis@entrata.com>)
Responses Re: Aggregate and many LEFT JOIN  (kimaidou <kimaidou@gmail.com>)
List pgsql-performance
Michael Lewis <mlewis@entrata.com> writes:
> Does the plan change significantly with this-
> set session work_mem='250MB';
> set session geqo_threshold = 20;
> set session join_collapse_limit = 20;

Yeah ... by my count there are 16 tables in this query, so raising
join_collapse_limit to 15 is not enough to ensure that the planner
considers all join orders.  Whether use of GEQO is a big problem
is harder to say, but it might be.

            regards, tom lane


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