Re: Conflict detection for update_deleted in logical replication

On Mon, Aug 25, 2025 at 10:06 AM Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> Attach the V65 patch set which addressed above and
> Shveta's comments[1].
>

Thank You for the patches, please find a few comments on v64 itself (I
think valid on v65 as well):

1) in resume_conflict_info_retention(), shall we rewrite the code as:

resume_conflict_info_retention(RetainDeadTuplesData *rdt_data)
{
if (TransactionIdIsValid(MyLogicalRepWorker->oldest_nonremovable_xid))
{
Assert(MySubscription->retentionactive);
reset_retention_data_fields(rdt_data);

/* process the next phase */
process_rdt_phase_transition(rdt_data, false);
return;
}

--rest of the code to start a transaction and update the catalog to
set retentionactive=true.
}

When 'MyLogicalRepWorker->oldest_nonremovable_xid' is valid, it either
means retention has not been stopped yet due to the inability to start
a txn or it is that stage of resume (subsequent calls) where catalog
has been updated and the launcher has initialized slot.xmin and
assigned it to oldest_nonremovable_xid. In both cases
'retentionactive' should be true by now and thus the Assert can be put
(as above). The dependency on 'wait_for_initial_xid' can be removed if
we do it like this.

2)
Also, I feel the code part which does txn and snapshot processing
(Start, Push, Pop, Commit, launcher-wakeup) and update catalog can be
shifted to one function and both stop_conflict_info_retention() and
resume_conflict_info_retention() can call it.

thanks
Shveta