Horton

Re: NOT IN subquery optimization

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
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: 2019-03-01T22:28:00Z
Lists: pgsql-hackers

Attachments

On Sat, 2 Mar 2019 at 05:44, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Andres Freund <andres@anarazel.de> writes:
> > I've not checked, but could we please make sure these cases are covered
> > in the regression tests today with a single liner?
>
> 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.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

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