Re: Proposal: Conflict log history table for Logical Replication

On Wed, May 6, 2026 at 4:31 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, May 6, 2026 at 3:01 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > On Wed, May 6, 2026 at 9:24 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> > >
> > > Few comments:
> > > 1) Currently we allow renaming of pg_conflict schema, this might be ok
> > > as we allow other sysem schema like pg_catalog and pg_toast also.
> > > postgres=# alter schema pg_conflict rename to test_conflict;
> > > ALTER SCHEMA
> > >
> >
> > I agree that we allow renaming other schemas including pg_toast, but I
> > am not sure if this is consciously made decision, see BUG #18281 ast
> > [1]. I don't favour allowing renaming pg_conflict for 2 reasons:
> >
> > 1) Because Postgres explicitly blocks renaming schemas to a name
> > starting with 'pg_'. If an admin accidentally renames 'pg_conflict' to
> > something else, they are permanently locked out from renaming it back.
> >
> > 2) While the core worker might survive a rename via OID lookups;
> > external scripts, extensions, and monitoring tools will likely
> > hardcode the 'pg_conflict' string. If the schema is renamed, these
> > tools will fail.
> >
>
> I think we shouldn't go out of our way to disallow superusers to
> rename pg_conflict schema similar to other cases. We can try to
> prevent hard-coding schema names where possible but not sure we can
> guarantee that nothing related to pg_conflict schema won't break as
> shown by you in the following similar case for pg_conflict.
>
> > One such example of scripts breaking is present event in Postgres. I
> > did the following, and most of psql commands started failing after
> > that due to hard-coded pg_catalog name in them.
> >
> > postgres=# alter schema pg_catalog rename to catalog_new;
> > ALTER SCHEMA
> >
> > postgres=# \d catalog_new.*
> > ERROR: relation "pg_catalog.pg_class" does not exist
> > LINE 5: FROM pg_catalog.pg_class c
> >
> > [1]: https://www.postgresql.org/message-id/flat/18281-5b1b6c5991d345aa%40postgresql.org

I can see pg_toast and pg_catalog schema also hard coded in couple of
places e.g.

listPartitionedTables()
{
if (!pattern)
appendPQExpBufferStr(&buf, " AND n.nspname <> 'pg_catalog'\n"
" AND n.nspname !~ '^pg_toast'\n"
" AND n.nspname <> 'information_schema'\n");
}

I will analyze which all places we are hardcoding, I think on server
side code we can easily avoid but from client side e.g. describe we
might need to invent a way to identify the schema name, or we might
have to store it somewhere in pg_subscription etc, I don't think we
should go that route.

--
Regards,
Dilip Kumar
Google