| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | "Li, Zheng" <zhelli(at)amazon(dot)com> |
| Cc: | "Finnerty, Jim" <jfinnert(at)amazon(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: NOT IN subquery optimization |
| Date: | 2019-02-27 00:24:26 |
| Message-ID: | CAKJS1f9o+f-xH8TGHJnuAM_RjjTxV6hTVOxiMKjrfdcjWiSzzA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 27 Feb 2019 at 13:05, Li, Zheng <zhelli(at)amazon(dot)com> wrote:
> -With the latest fix (for the empty table case), our patch does the transformation as long as the outer is non-nullable regardless of the inner nullability, experiments show that the results are always faster.
Hi Zheng,
I'm interested to know how this works without testing for inner
nullability. If any of the inner side's join exprs are NULL then no
records can match. What do you propose to work around that?
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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