Re: Conflict detection for update_deleted in logical replication

On Mon, Aug 25, 2025 at 12:09 PM shveta malik <shveta.malik@gmail.com> wrote:
>
> On Mon, Aug 25, 2025 at 10:06 AM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.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):
>

All previously reported bugs seem to be fixed on the latest patch.

Please find a few comments on v65 though:

1)

 The comment atop adjust_xid_advance_interval() says:
~~
* The interval is reset to the lesser of 100ms and
* max_conflict_retention_duration once there is some activities on the node.
~~

 But we are not doing min of the 2 values when we find new-xid (i.e.
we see activity on node)

                /*
                 * A new transaction ID was found or the interval is not yet
                 * initialized, so set the interval to the minimum value.
                 */
                rdt_data->xid_advance_interval = MIN_XID_ADVANCE_INTERVAL;

2)
* max_conflict_retention_duration once there is some activities on the node.

activities-->activity

3)
On putting some logs, when all subs stopped retention, the values are:

LOG:  ***** can_advance_xmin:1, retention_inactive:0, xmin:0
LOG:  ***** can_advance_xmin:1, retention_inactive:0, xmin:0

can_advance_xmin:1 and xmin=0 seems contradictory. Can we do something
here to improve this situation?

4)
Also I fail to think of a scenario where retention_inactive will be
useful as everything seems to be handled using can_advance_xmin
already i.e. slot is updated to have invalid xmin only through
'can_advance_xmin' without relying on retention_inactive.

thanks
Shveta