Re: Query planner cost estimate less than the sum of its parts? - Mailing list pgsql-performance

"Scott Carey" <scott@richrelevance.com> writes:

> Certainly, a cost estimate that is ... LESS than one of the sub sections of
> the query is wrong.   This was one hell of a broken query, but it at least
> should have taken an approach that was not a nested loop, and I'm curious if
> that choice was due to a bad estimate here.
>
> Nested Loop IN Join  (cost=0.00..3850831.86 rows=128266 width=8)

Because it's an IN join it doesn't have to run the inner join to completion.
Once it finds a match it can return the outer tuple and continue to the next
outer tuple.

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  Gregory Stark
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