Horton

Re: NOT IN subquery optimization

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Richard Guo <riguo@pivotal.io>, "Li, Zheng" <zhelli@amazon.com>, "Finnerty, Jim" <jfinnert@amazon.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-03-01T22:57:58Z
Lists: pgsql-hackers 
David Rowley <david.rowley@2ndquadrant.com> writes:
> On Sat, 2 Mar 2019 at 05:44, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I'm not sure if the second one is actually a semantics bug or just a
>> misoptimization?  But yeah, +1 for putting in some simple tests for
>> corner cases right now.  Anyone want to propose a specific patch?

> The second is just reducing the planner's flexibility to produce a
> good plan.  The first is a bug. Proposed regression test attached.

LGTM, pushed.

			regards, tom lane

Commits

  1. Check we don't misoptimize a NOT IN where the subquery returns no rows.