| From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
|---|---|
| To: | Tender Wang <tndrwang(at)gmail(dot)com>, Richard Guo <guofenglinux(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, 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: | 2025-02-26 10:54:08 |
| Message-ID: | c1f7717b6dbd80fa3b05c8fc90a2b3969d7f21f2.camel@cybertec.at |
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| Lists: | pgsql-hackers |
On Wed, 2025-02-26 at 18:08 +0800, Tender Wang 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)
That is true, but I don't see how it leads to an anti-join
without further consideration. Perhaps you mean something
else by "pull up"...
Yours,
Laurenz Albe
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