Re: Support "Right Semi Join" plan shapes

Richard Guo <guofenglinux@gmail.com>

From: Richard Guo <guofenglinux@gmail.com>

To: Alena Rybakina <lena.ribackina@yandex.ru>

Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, wenhui qiu <qiuwenhuifx@gmail.com>, vignesh C <vignesh21@gmail.com>

Date: 2024-03-05T02:44:11Z

Lists: pgsql-hackers

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Support "Right Semi Join" plan shapes
- aa86129e19d7 18.0 landed
Fix neqjoinsel's behavior for semi/anti join cases.
- 7ca25b7de6ae 11.0 cited

On Tue, Jan 30, 2024 at 2:51 PM Alena Rybakina <lena.ribackina@yandex.ru>
wrote:

> I have reviewed your patch and I think it is better to add an Assert for
> JOIN_RIGHT_SEMI to the ExecMergeJoin and ExecNestLoop functions to
> prevent the use of RIGHT_SEMI for these types of connections (NestedLoop
> and MergeJoin).

Hmm, I don't see why this is necessary.  The planner should already
guarantee that we won't have nestloops/mergejoins with right-semi joins.

Thanks
Richard