Re: Design of pg_stat_subscription_workers vs pgstats

On Tue, Feb 22, 2022 at 11:15 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> I've attached a patch that changes pg_stat_subscription_workers view.
> It removes non-cumulative values such as error details such as
> error-XID and the error message from the view, and consequently the
> view now has only cumulative statistics counters: apply_error_count
> and sync_error_count. Since the new view name is under discussion I
> temporarily chose pg_stat_subscription_activity.
>

Few comments:
=============
1.
--- a/src/backend/catalog/system_functions.sql
+++ b/src/backend/catalog/system_functions.sql
@@ -637,11 +637,9 @@ REVOKE EXECUTE ON FUNCTION
pg_stat_reset_single_table_counters(oid) FROM public;

REVOKE EXECUTE ON FUNCTION
pg_stat_reset_single_function_counters(oid) FROM public;

-REVOKE EXECUTE ON FUNCTION pg_stat_reset_replication_slot(text) FROM public;
-
-REVOKE EXECUTE ON FUNCTION pg_stat_reset_subscription_worker(oid) FROM public;
+REVOKE EXECUTE ON FUNCTION
pg_stat_reset_single_subscription_counters(oid) FROM public;

-REVOKE EXECUTE ON FUNCTION pg_stat_reset_subscription_worker(oid,
oid) FROM public;
+REVOKE EXECUTE ON FUNCTION pg_stat_reset_replication_slot(text) FROM public;

Is there a need to change anything about
pg_stat_reset_replication_slot() in this patch?

2. Do we still need to use LATERAL in the view's query?

3. Can we send error stats pgstat_report_stat() as that will be called
via proc_exit() path. We can set the phase (apply/sync) in
apply_error_callback_arg and then use that to send the appropriate
message. I think this will obviate the need for try..catch.

--
With Regards,
Amit Kapila.