Horton

Re: Forbid to DROP temp tables of other sessions

Steven Niu <niushiji@gmail.com>

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From: Steven Niu <niushiji@gmail.com>
To: Daniil Davydov <3danissimo@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: 2025-03-17T13:28:50Z
Lists: pgsql-hackers

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  1. pg_basebackup: Add missing PQclear in error path


在 2025/3/17 18:56, Daniil Davydov 写道:
> Hi,
> 
> On Mon, Mar 17, 2025 at 5:33 PM Steven Niu <niushiji@gmail.com> wrote:
>>
>> I mean RangeVarGetRelidExtended(), you deleted the following code:
>>
>> if (!OidIsValid(myTempNamespace))
>>              relId = InvalidOid; /* this probably can't happen? */
> 
> Hm, I got it. Let's start with the fact that the comment "this
> probably can't happen?" is incorrect. Even if we don't have a
> temporary namespace in our session, we still can specify "pg_temp_N"
> in the psql query.
> Next, if relation->schemaname is pg_temp, then we firstly call
> LookupExplicitNamespace, where you can find if
> (!OidIsValid(myTempNamespace)) check.
> 
> --
> Best regards,
> Daniil Davydov

If the (relation->relpersistence == RELPERSISTENCE_TEMP) can ensure the 
myTempNamespace is always valid, then my comment can be ignored. 
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? */
  else
  {
    if (relation->schemaname)
    {
      namespaceId = LookupExplicitNamespace(relation->schemaname, 
missing_ok);
      if (namespaceId != myTempNamespace)
      {
          ereport(ERROR,
                  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                   errmsg("could not access temporary relations of other 
sessions")));
      }
   }
   else
   {
      namespaceId = myTempNamespace;
      Assert(OidIsValid(namespaceId));
   }
   if (missing_ok && !OidIsValid(namespaceId))
      relId = InvalidOid;
   else
      relId = get_relname_relid(relation->relname, namespaceId);
  }
...
...

Thanks,
Steven