Re: [Patch] add new parameter to pg_replication_origin_session_setup

On Wed, Feb 11, 2026 at 3:41 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Feb 4, 2026 at 11:32 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > On Wed, Feb 4, 2026 at 12:38 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> > >
> >
> > >
> > > The second patch rearranges the if-else statements to check those
> > > conditions. I found the current logic hard to follow, this makes them
> > > feel more natural, in my opinion at least.
> >
> > I’m not fully convinced that it makes the code clearer or better to
> > understand. For example, consider the following error case:
> >
> > else if (curstate->acquired_by == 0 && curstate->refcount > 0)
> > ereport(ERROR,
> > (errcode(ERRCODE_OBJECT_IN_USE),
> > errmsg("replication origin with ID %d is already active
> > in another process",
> > curstate->roident)));
> >
> >
> > The condition was self explanatory earlier. The condition has now been
> > rewritten (or reduced) to:
> > if (acquired_by == 0 && curstate->refcount > 0)
> >
> > However, this is not exactly the same as the earlier logic. On closer
> > inspection, the condition 'curstate->acquired_by == 0', while no
> > longer stated explicitly, was implicitly guaranteed by the preceding
> > error block:
> >
> > if (curstate->acquired_by != 0)
> > ERROR;
> >
> > One way to make this clearer would be to structure the logic as:
> >
> > if (curstate->acquired_by != 0)
> > ERROR;
> > else if (curstate->refcount > 0)
> > ERROR;
> >
> > Even then, it is still not clear why this error (the case where
> > curstate->refcount > 0 and curstate->acquired_by == 0) is raised only
> > when acquired_by == 0, or how the same situation is expected to be
> > handled when acquired_by != 0. The earlier code was clearer in this
> > regard (at least to me), as it first handled the
> > 'curstate->acquired_by != acquired_by' case, making the overall logic
> > somehow easier to understand. Perhaps we can try by adding a comment
> > or restructure in some other way if possible and needed?
> >
>
> I see your point but one advantage with the proposed code change is
> that it started to appear that we can extend this part of code easily
> in the future as it separates most of the handling related to when a
> user has given acquired_by parameter's value as zero and non-zero.

Okay, yes. So I am okay with it. The slight change I suggested (if to
else-if) and a comment will make it more clean.

>
> > > It has one user-visible
> > > effect: If you call the function with acquired_pid != 0 and the origin
> > > has no state slot, *and* there are no free slots, you previously got
> > > this error:
> > >
> > > postgres=# select pg_replication_origin_session_setup('other', 123);
> > > ERROR: could not find free replication state slot for replication
> > > origin with ID 2
> > > HINT: Increase "max_active_replication_origins" and try again.
> > >
> > > Now you get this:
> > >
> > > postgres=# select pg_replication_origin_session_setup('other', 123);
> > > ERROR: cannot use PID 123 for inactive replication origin with ID 2
> > >
> > > Both error messages are more or less appropriate in that situation, but
> > > I think the new behavior is slightly better. The fact that the origin is
> > > inactive feels like the bigger problem here.
> >
> > I am okay with this change though. Let's see what others have to say.
> >
>
> Either message is fine with me in this situation.
>
> --
> With Regards,
> Amit Kapila.