Re: Collect statistics about conflicts in logical replication

On Wed, Aug 28, 2024 at 9:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Aug 28, 2024 at 11:43 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > Thanks for the patch. Just thinking out loud, since we have names like
> > 'apply_error_count', 'sync_error_count' which tells that they are
> > actually error-count, will it be better to have something similar in
> > conflict-count cases, like 'insert_exists_conflict_count',
> > 'delete_missing_conflict_count' and so on. Thoughts?
> >
>
> It would be better to have conflict in the names but OTOH it will make
> the names a bit longer. The other alternatives could be (a)
> insert_exists_confl_count, etc. (b) confl_insert_exists_count, etc.
> (c) confl_insert_exists, etc. These are based on the column names in
> the existing view pg_stat_database_conflicts [1]. The (c) looks better
> than other options but it will make the conflict-related columns
> different from error-related columns.
>
> Yet another option is to have a different view like
> pg_stat_subscription_conflicts but that sounds like going too far.
>
> [1] - https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW

Option (c) looked good to me.

Removing the suffix "_count" is OK. For example, try searching all of
Chapter 27 ("The Cumulative Statistics System") [1] for columns
described as "Number of ..." and you will find that a "_count" suffix
is used only rarely.

Adding the prefix "confl_" is OK. As mentioned, there is a precedent
for this. See "pg_stat_database_conflicts" [2].

Mixing column names where some have and some do not have "_count"
suffixes may not be ideal, but I see no problem because there are
precedents for that too. E.g. see "pg_stat_replication_slots" [3], and
"pg_stat_all_tables" [4].

======
[1] https://www.postgresql.org/docs/devel/monitoring-stats.html
[2] https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW
[3] https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW
[4] https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW

Kind Regards,
Peter Smith.
Fujitsu Australia