Re: Proposal: Conflict log history table for Logical Replication

On Thu, Dec 11, 2025 at 5:04 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Tue, Dec 9, 2025 at 8:41 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > >
> > Here is the updated version of patch
> > What has changed
> > 1. Table is created using create_heap_with_catalog() instead of SPI as
> > suggested by Sawada-San and Amit Kapila.
> > 2. Validated the table schema after acquiring the lock before
> > preparing/inserting conflict tuples for defects raised by Vignesh.
> > 3. Bug fixes raised by Shweta (segfault)
> > 3. Comments from Peter (except exposing namespace in \dRs+, it's still pending.
> >
>
> Thanks for the patch.
> I tested all conflict-types on this version, they (basic scenarios)
> seem to work well. Except only that key-RI pending issue, other issues
> seem to be addressed. I will start with code-review now.
>
> Few observations:
>
> 1)
> \dRs+ shows 'Conflict log table' without namespace, this could be
> confusing if the same table exists in multiple schemas.

Yeah this is not yet fixed comments, will fix in next version.

> 2)
> When we do below:
> alter subscription sub1 SET (conflict_log_table=clt2);
>
> the previous conflict log table is dropped. Is this behavior
> intentional and discussed/concluded earlier? It’s possible that a user
> may want to create a new conflict log table for future events while
> still retaining the old one for analysis. If the subscription itself
> is dropped, then dropping the CLT makes sense, but I’m not sure this
> behavior is intended for ALTER SUBSCRIPTION. I do understand that
> once we unlink CLT from subscription, later even DROP subscription
> cannot drop it, but user can always drop it when not needed.
>
> If we plan to keep existing behavior, it should be clearly documented
> in a CAUTION section, and the command should explicitly log the table
> drop.

Yeah we discussed this behavior and the conclusion was we would
document this behavior and its user's responsibility to take necessary
backup of the conflict log table data if they are setting a new log
table or NONE for the subscription.

--
Regards,
Dilip Kumar
Google