Re: Proposal: Conflict log history table for Logical Replication

On Thu, 25 Jun 2026 at 19:15, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Thu, Jun 25, 2026 at 6:37 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Thu, Jun 25, 2026 at 6:30 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> > >
> > > On Thu, Jun 25, 2026 at 4:57 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > >
> > >
> > > > 2.
> > > > @@ -2482,6 +2681,8 @@ DropSubscription(DropSubscriptionStmt *stmt,
> > > > bool isTopLevel)
> > > > deleteDependencyRecordsFor(SubscriptionRelationId, subid, false);
> > > > deleteSharedDependencyRecordsFor(SubscriptionRelationId, subid, 0);
> > > >
> > > > + drop_sub_conflict_log_table(subid, subname, subconflictlogrelid);
> > > >
> > > > It would be better to drop the table before cleaning up the dependency
> > > > record. Right now, it is okay even in current order because dependency
> > > > removal is trying to remove where subid is depender.
> > >
> > > So whats your suggestion change it now or not? I feel either way is fine.
> > >
> >
> > Let's change now itself.
>
> PFA, updated version of the patch, fixes all the comments of V57

Thanks for the updated patches.
Currently, we allow an empty string for conflict_log_destination:
postgres=# CREATE SUBSCRIPTION sub1 CONNECTION 'dbname=postgres
host=localhost port=5432' PUBLICATION pub1 WITH
(conflict_log_destination = '');
NOTICE: created replication slot "sub1" on publisher
CREATE SUBSCRIPTION

postgres=# SELECT subconflictlogdest FROM pg_subscription WHERE
subname = 'sub1';
subconflictlogdest
--------------------
log
(1 row)

However, this is inconsistent with the behavior of the other
subscription options, which all reject an empty string. For example:
postgres=# CREATE SUBSCRIPTION sub2 ... WITH (origin = '');
ERROR: unrecognized origin value: ""

postgres=# CREATE SUBSCRIPTION sub2 ... WITH (streaming = '');
ERROR: streaming requires a Boolean value or "parallel"

postgres=# CREATE SUBSCRIPTION sub2 ... WITH (copy_data = '');
ERROR: copy_data requires a Boolean value

postgres=# CREATE SUBSCRIPTION sub2 ... WITH (wal_receiver_timeout = '');
ERROR: invalid value for parameter "wal_receiver_timeout": ""

postgres=# CREATE SUBSCRIPTION sub2 ... WITH (max_retention_duration = '');
ERROR: max_retention_duration requires an integer value

postgres=# CREATE SUBSCRIPTION sub2 ... WITH (slot_name = '');
ERROR: replication slot name "" is too short

I think conflict_log_destination should behave consistently with the
other subscription options and reject an empty string rather than
silently treating it as log. If there is a specific reason for
accepting '', it would be good to document that behavior.

Regards,
Vignesh