Re: [PATCH] Support automatic sequence replication

Hi,

On Fri, Feb 13, 2026 at 4:56 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Fri, Feb 13, 2026 at 4:48 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Fri, Feb 13, 2026 at 11:39 AM Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
> > >
> > > Is this expected behavior?
> > >
> > > 1) Publisher:
> > >
> > > create sequence t1_seq;
> > > create table t1 (id int default nextval('t1_seq') primary key, a int);
> > >
> > > create publication t1_pub for table t1;
> > > create publication t1_seq_pub for all sequences;
> > >
> > > 2) Subscriber:
> > >
> > > create sequence t1_seq;
> > > create table t1 (id int default nextval('t1_seq') primary key, a int);
> > >
> > > create subscription t1_sub connection 'host=127.0.0.1 port=37500 dbname=test user=$USER' publication t1_pub with (create_slot = false, slot_name = 't1_sub');
> > > create subscription t1_seq_sub connection 'host=127.0.0.1 port=37500 dbname=test user=$USER' publication t1_seq_pub with (create_slot = false, slot_name = 't1_seq_sub');
> > >
> > > select * from pg_subscription_rel;
> > > select * from pg_sequences;
> > >
> > > 3) Publisher:
> > >
> > > insert into t1(a) values(10);
> > > select * from pg_sequences;
> > >
> > > 4) Subscriber:
> > >
> > > select * from pg_sequences; -- in sync with publisher.
> > > insert into t1(a) values(20);
> > > select * from pg_sequences; -- the sequence gets deviated from publisher.
> > >
> > > After a few minutes, re-running the above shows that the sequence value is reset to match the publisher. However, any new insert on the subscriber fails:
> > >
> > > insert into t1(a) values(30);
> > > ERROR: 23505: duplicate key value violates unique constraint "t1_pkey"
> > > DETAIL: Key (id)=(2) already exists.
> > > SCHEMA NAME: public
> > > TABLE NAME: t1
> > > CONSTRAINT NAME: t1_pkey
> > >
> > > --
> > >
> > > Automatic sequence replication resets the last_value on the subscriber to match the publisher, which leads to duplicate key conflicts and prevents further inserts on the subscriber.
> > >
> >
> > This is possible even without automatic sequence replication, say when
> > the user uses REFRESH SEQUENCES command just before values(30). This
> > is because sequence replication is mainly provided for upgrade
> > purposes where sequences can be made up-to-date before upgrade. We
> > should update this information in docs, if not already present.
> >
> Yes. It is not present currently.
>
> > Having said that, we can possibly detect such synchronization as the
> > sequence_update type of conflict and don't allow it to update on
> > subscribers but that will be a separate patch.
> >
>
> I agree with this. It will not be in scope of the current patch.

Okay, agreed - it can be handled as a separate item.

--
With Regards,
Ashutosh Sharma.