On Mon, Jun 21, 2021 at 4:17 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, Jun 21, 2021 at 11:19 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
>
> I think we should store the input from the user (like disable_on_error
> flag or xid to skip) in the system catalog pg_subscription and send
> the error information (subscrtion_id, rel_id, xid of failed xact,
> error_code, error_message, etc.) to the stats collector which can be
> used to display such information via a stat view.
>
> The disable_on_error flag handling could be that on error it sends the
> required error info to stats collector and then updates the subenabled
> in pg_subscription. In rare conditions, where we are able to send the
> message but couldn't update the subenabled info in pg_subscription
> either due to some error or server restart, the apply worker would
> again try to apply the same change and would hit the same error again
> which I think should be fine because it will ultimately succeed.
>
> The skip xid handling will also be somewhat similar where on an error,
> we will send the error information to stats collector which will be
> displayed via stats view. Then the user is expected to ask for skip
> xid (Alter Subscription ... SKIP <xid_value>) based on information
> displayed via stat view. Now, the apply worker can skip changes from
> such a transaction, and then during processing of commit record of the
> skipped transaction, it should update xid to invalid value, so that
> next time that shouldn't be used. I think it is important to update
> xid to an invalid value as part of the skipped transaction because
> otherwise, after the restart, we won't be able to decide whether we
> still want to skip the xid stored for a subscription.
>
One minor detail I missed in the above sketch for skipped transaction
feature was that actually we only need replication origin state from
the commit record of the skipped transaction and then I think we need
to start a transaction, update the xid value to invalid, set the
replication origin state and commit that transaction.
--
With Regards,
Amit Kapila.