Horton

Re: Forbid to DROP temp tables of other sessions

Daniil Davydov <3danissimo@gmail.com>

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From: Daniil Davydov <3danissimo@gmail.com>
To: Steven Niu <niushiji@gmail.com>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Andres Freund <andres@anarazel.de>, Thomas Munro <thomas.munro@gmail.com>, Rafia Sabih <rafia.pghackers@gmail.com>, Michael Paquier <michael@paquier.xyz>, Tom Lane <tgl@sss.pgh.pa.us>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2025-03-17T17:04:15Z
Lists: pgsql-hackers

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  1. pg_basebackup: Add missing PQclear in error path

Hi,

On Mon, Mar 17, 2025 at 8:29 PM Steven Niu <niushiji@gmail.com> wrote:
>
> If the (relation->relpersistence == RELPERSISTENCE_TEMP) can ensure the
> myTempNamespace is always valid, then my comment can be ignored.

No, even if we see a temporary table in RangeVarGetRelidExtended,
MyTempNamespace still can be `InvalidOid` (I mentioned it in the
previous letter).
Thus, comment like "this probably can't happen?" should be removed.

> Otherwise I think the modified RangeVarGetRelidExtended() should keep
> check of myTempNamespace, like this:
>
> if (relation->relpersistence == RELPERSISTENCE_TEMP)
> {
>    Oid namespaceId;
>
>   if (!OidIsValid(myTempNamespace))
>       relId = InvalidOid; /* this probably can't happen? */
>  ...

OK, let's assume that MyTempNamespace == InvalidOid and caller
specified "pg_temp_N" in his query. In this case we want to throw an
error, because access to the other temp tables is prohibited.
If we keep code like "if (!OidIsValid(myTempNamespace)) => relId =
InvalidOid", eventually the caller will get an error "relation ...
does not exist".
Yes, we have saved the caller from making mistakes, but we are giving
the wrong error message.

In my realization the caller will get the correct error message, and I
still think that we should keep v3 patch logic.

--
Best regards,
Daniil Davydov