Re: Assert failure due to "drop schema pg_temp_3 cascade" for temporary tables and \d+ is not showing any info after drooping temp table schema

On Fri, 10 Jan 2020 at 16:37, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Fri, Jan 10, 2020 at 05:01:25PM +0900, Michael Paquier wrote:
> > This makes me wonder how much we should try to outsmart somebody which
> > puts the catalogs in such a inconsistent state. Hmm. Perhaps at the
> > end autovacuum should just ignore such entries and just don't help the
> > user at all as this also comes with its own issues with the storage
> > level as well as smgr.c uses rd_backend. And if the user plays with
> > temporary namespaces like that with superuser rights, he likely knows
> > what he is doing. Perhaps not :D, in which case autovacuum may not be
> > the best thing to decide that. I still think we should make the log
> > of autovacuum.c for orphaned relations more careful with its coding
> > though, and fix it with the previous patch. The documentation of
> > isTempNamespaceInUse() could gain in clarity, just a nit from me while
> > looking at the surroundings. And actually I found an issue with its
> > logic, as the routine would not consider a temp namespace in use for a
> > session's own MyBackendId. As that's only used for autovacuum, this
> > has no consequence, but let's be correct in hte long run.
> >
> > And this gives the attached after a closer lookup. Thoughts?
>
> Thinking more about it, this has a race condition if a temporary
> schema is removed after collecting the OIDs in the drop phase. So the
> updated attached is actually much more conservative and does not need
> an update of the log message, without giving up on the improvements
> done in v11~. In 9.4~10, the code of the second phase relies on
> GetTempNamespaceBackendId() which causes an orphaned relation to not
> be dropped in the event of a missing namespace. I'll just leave that
> alone for a couple of days now..
> --

Thanks for the patch. I am not getting any crash but \d is not showing
any temp table if we drop temp schema and create again temp table.

postgres=# create temporary table test1 (a int);
CREATE TABLE
postgres=# \d
List of relations
Schema | Name | Type | Owner
-----------+-------+-------+----------
pg_temp_3 | test1 | table | mahendra
(1 row)

postgres=# drop schema pg_temp_3 cascade ;
NOTICE: drop cascades to table test1
DROP SCHEMA
postgres=# \d
Did not find any relations.
postgres=# create temporary table test1 (a int);
CREATE TABLE
postgres=# \d
Did not find any relations.
postgres=#

Thanks and Regards
Mahendra Singh Thalor
EnterpriseDB: http://www.enterprisedb.com