Re: Proposal: Conflict log history table for Logical Replication

On Fri, Dec 19, 2025 at 5:35 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> On Thu, Dec 18, 2025 at 8:09 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > On Tue, Dec 16, 2025 at 9:51 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > On Mon, Dec 15, 2025 at 5:11 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > >
> > > We could do this as a first step. See the proposal in email [1] where
> > > we have discussed having two options instead of one. The first option
> > > will be conflict_log_format and the values would be log and table. In
> > > this case, the table would be an internally generated one.
> > >
> > > [1] - https://www.postgresql.org/message-id/CAA4eK1KwqE2y%3D_k5Xc%3Def0S5JXG2x%3DoeWpDJ%2B%3D5k6Anzaw2gdw%40mail.gmail.com
> >
> > So I have put more thought on this and here is what I am proposing
> >
> > 1) Subscription Parameter: Son in first version the subscription
> > parameter will be named 'conflict_log_format' which will accept
> > 'log/table/both' default option would be log.
> > 2) If conflict_log_format = log is provided then we do not need to do
> > anything as this would work by default
> > 3) If conflict_log_format = table/both is provided then we will
> > generate a internal table name i.e. conflict_log_table_$subid$ and the
> > table will be created in the current schema
> > 4) in pg_subscription we will still keep 2 field a) namespace id of
> > the conflict log table b) the conflict log format = 'log/table'both'
> > 5) If option is table/both the name can be generated on the fly
> > whether we are creating the table or inserting conflict into the
> > table.
>
> IIUC, previously you had a "none" value which was a way to "turn off"
> any CLT previously defined. How can users do that now with
> log/table/both? Would they have to reassign (the default) "log"? That
> seems a bit strange.

Previously we were supporting only conflict log tables and by default
it was always sent to log. And "none" was used for clearing the
conflict log table option; it was never meant for not logging anywhere
it was meant to say that there is no conflict log table. Now also we
can have another option as none but I intentionally avoided it
considering we want to support the case where we don't want to log it
at all, maybe that's not a bad idea either. Let's see what others
think about it.

--
Regards,
Dilip Kumar
Google