Re: Schema variables - new implementation for Postgres 15

> On Sun, Mar 26, 2023 at 07:32:05PM +0800, Julien Rouhaud wrote:
> Hi,
>
> I just have a few minor wording improvements for the various comments /
> documentation you quoted.

Talking about documentation I've noticed that the implementation
contains few limitations, that are not mentioned in the docs. Examples
are WITH queries:

WITH x AS (LET public.svar = 100) SELECT * FROM x;
ERROR: LET not supported in WITH query

and using with set-returning functions (haven't found any related tests).

Another small note is about this change in the rowsecurity:

/*
- * For SELECT, UPDATE and DELETE, add security quals to enforce the USING
- * policies. These security quals control access to existing table rows.
- * Restrictive policies are combined together using AND, and permissive
- * policies are combined together using OR.
+ * For SELECT, LET, UPDATE and DELETE, add security quals to enforce the
+ * USING policies. These security quals control access to existing table
+ * rows. Restrictive policies are combined together using AND, and
+ * permissive policies are combined together using OR.
*/

From this commentary one may think that LET command supports row level
security, but I don't see it being implemented. A wrong commentary?