| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Richard Guo <riguo(at)pivotal(dot)io>, "Li, Zheng" <zhelli(at)amazon(dot)com>, "Finnerty, Jim" <jfinnert(at)amazon(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: NOT IN subquery optimization |
| Date: | 2019-03-01 16:44:17 |
| Message-ID: | 31411.1551458657@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On March 1, 2019 4:53:03 AM PST, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
>> On Fri, 1 Mar 2019 at 15:27, Richard Guo <riguo(at)pivotal(dot)io> wrote:
>>> 1. The patch would give wrong results when the inner side is empty.
>>> 2. Because of the new added predicate 'OR (var is NULL)', we cannot
>>> use hash join or merge join to do the ANTI JOIN.
> 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?
regards, tom lane
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