Re: Proposal: Conflict log history table for Logical Replication

On Fri, Dec 5, 2025 at 10:47 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Fri, Dec 5, 2025 at 9:24 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
>
> > 2) Is there a way to unset the conflict log table after we create the
> > subscription with conflict_log_table option
>
> IMHO we can use ALTER SUBSCRIPTION...WITH(conflict_log_table='') so
> unset? What do others think about it?
>

We already have a syntax: ALTER SUBSCRIPTION name SET (
subscription_parameter [= value] [, ... ] ) which can be used to
set/unset this new subscription option.

> > 3) Any reason why this table should not be allowed to add to a publication:
> > + /* Can't be conflict log table */
> > + if (IsConflictLogTable(RelationGetRelid(targetrel)))
> > + ereport(ERROR,
> > + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> > + errmsg("cannot add relation \"%s.%s\"
> > to publication",
> > +
> > get_namespace_name(RelationGetNamespace(targetrel)),
> > +
> > RelationGetRelationName(targetrel)),
> > + errdetail("This operation is not
> > supported for conflict log tables.")));
> >
> > Is the reason like the same table can be a conflict table in the
> > subscriber and prevent corruption in the subscriber
>
> The main reason was that, since these tables are internally created
> for maintaining the conflict information which is very much internal
> node specific details, so there is no reason someone want to replicate
> those tables, so we blocked it with ALL TABLES option and then based
> on suggestion from Shveta we blocked it from getting added to
> publication as well. So there is no strong reason to disallow from
> forcefully getting added to publication OTOH there is no reason why
> someone wants to do that considering those are internally managed
> tables.
>

I also don't see any reason to allow such internal tables to be
replicated. So, it is okay to prohibit them for now. If we see any use
case, we can allow it.

--
With Regards,
Amit Kapila.