| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Tender Wang <tndrwang(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Anti join confusion |
| Date: | 2025-03-03 07:34:45 |
| Message-ID: | CAMbWs48cKN5u2Q6iRCb=bUz6u_2tKGVf=czQRtNVw40-07PwCw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Feb 26, 2025 at 7:09 PM Tender Wang <tndrwang(at)gmail(dot)com> wrote:
> Recently, I found Greenplum implement pull-up NOT IN subquery. They have the below comments in their codes:
>
> We normalize NOT subqueries using the following axioms:
> *
> * val NOT IN (subq) => val <> ALL (subq)
>
> Richard, do you have an impression about this?
I vaguely recall that Greenplum converts NOT IN to some form of join
in certain cases, but I can't remember the details.
Thanks
Richard
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