Thread

Re: Proposal: Conflict log history table for Logical Replication

Dilip Kumar <dilipbalaut@gmail.com> — 2025-12-17T04:28:52Z

On Tue, Dec 16, 2025 at 10:33 AM shveta malik <shveta.malik@gmail.com> wrote:

> The OID check may be unreliable, as mentioned in the comment. I tested
> this by dropping and recreating information_schema, and observed that
> after recreation it became eligible for publication because its relid
> no longer falls under FirstNormalObjectId.  Steps:
>
> ****Pub****:
> create publication pub1;
> ALTER PUBLICATION pub1 ADD TABLE information_schema.sql_sizing;
> select * from information_schema.sql_sizing where sizing_id=97;
>
> ****Sub****:
> create subscription sub1 connection '...' publication pub1 with
> (copy_data=false);
> select * from information_schema.sql_sizing where sizing_id=97;
>
> ****Pub****:
> alter table information_schema.sql_sizing replica identity full;
> --this is not replicated.
> UPDATE information_schema.sql_sizing set supported_value=12 where sizing_id=97;
>
> ****Sub****:
> postgres=# select supported_value from information_schema.sql_sizing
> where sizing_id=97;
>  supported_value
> -----------------
>               0
>
> ~~
>
> Then drop and recreate and try to perform the above update again, it
> gets replicated:
>
> drop schema information_schema cascade;
> ./psql -d postgres -f ./../../src/backend/catalog/information_schema.sql -p 5433
>
> ****Pub****:
> ALTER PUBLICATION pub1 ADD TABLE information_schema.sql_sizing;
> select * from information_schema.sql_sizing where sizing_id=97;
> alter table information_schema.sql_sizing replica identity full;
> --This is replicated
> UPDATE information_schema.sql_sizing set supported_value=14 where sizing_id=97;
>
> ****Sub****:
> --This shows supported_value as 14
> postgres=# select supported_value from information_schema.sql_sizing
> where sizing_id=97;
>  supported_value
> -----------------
>               14

Hmm, I might be missing something what why we do not want to publish
which is in information_shcema, especially when the internally created
schema is dropped then user can create his own schema with name
information-schema and create a bunch of tables in that so why do we
want to block those?  I mean the example you showed here is pretty
much like a user created schema and table no? Or am I missing
something important?

-- 
Regards,
Dilip Kumar
Google