Re: Weird row estimate - Mailing list pgsql-performance

From Tom Lane
Subject Re: Weird row estimate
Date
Msg-id 2393.1184186131@sss.pgh.pa.us
Whole thread Raw
In response to Weird row estimate  (Marc Cousin <mcousin@sigma.fr>)
Responses Re: Weird row estimate  (Marc Cousin <mcousin@sigma.fr>)
List pgsql-performance
Marc Cousin <mcousin@sigma.fr> writes:
> Nevertheless, shouldn't the third estimate be smaller or equal to the sum of the two others ?

The planner's estimation for subplan conditions is pretty primitive
compared to joinable conditions.  When you add the OR, it's no longer
possible to treat the IN like a join, and everything gets an order of
magnitude dumber :-(

It might be worth trying this as a UNION of the two simple queries.

            regards, tom lane

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