Re: Conflict detection and logging in logical replication

On Mon, Jul 29, 2024 at 11:44 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Friday, July 26, 2024 7:34 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Thu, Jul 25, 2024 at 4:12 PM Amit Kapila <amit.kapila16@gmail.com>
> > wrote:
> > > >
> > A few more comments:
>
> Thanks for the comments.
>
> > 1.
> > For duplicate key, the patch reports conflict as following:
> > ERROR:  conflict insert_exists detected on relation "public.t1"
> > 2024-07-26 11:06:34.570 IST [27800] DETAIL:  Key (c1)=(1) already exists in
> > unique index "t1_pkey", which was modified by origin 1 in transaction 770 at
> > 2024-07-26 09:16:47.79805+05:30.
> > 2024-07-26 11:06:34.570 IST [27800] CONTEXT:  processing remote data for
> > replication origin "pg_16387" during message type "INSERT" for replication
> > target relation "public.t1" in transaction 742, finished at 0/151A108
> >
> > In detail, it is better to display the origin name instead of the origin id. This will
> > be similar to what we do in CONTEXT information.
>
>
> Agreed. Before modifying this, I'd like to confirm the message style in the
> cases where origin id may not have a corresponding origin name (e.g., if the
> data was modified locally (id = 0), or if the origin that modified the data has
> been dropped). I thought of two styles:
>
> 1)
> - for local change: "xxx was modified by a different origin \"(local)\" in transaction 123 at 2024.."
> - for dropped origin: "xxx was modified by a different origin \"(unknown)\" in transaction 123 at 2024.."
>
> One issue for this style is that user may create an origin with the same name
> here (e.g. "(local)" and "(unknown)").
>
> 2)
> - for local change: "xxx was modified locally in transaction 123 at 2024.."
>

This sounds good.

> - for dropped origin: "xxx was modified by an unknown different origin 1234 in transaction 123 at 2024.."
>

For this one, how about: "xxx was modified by a non-existent origin in
transaction 123 at 2024.."?

Also, in code please do write comments when each of these two can occur.

--
With Regards,
Amit Kapila.