Re: Enhance statistics reset functions to return reset timestamp

On Fri, Aug 08, 2025 at 01:18:39PM +0900, Shinya Kato wrote:
> The following functions have been modified to return a TIMESTAMP WITH
> TIME ZONE value indicating when the statistics were reset:
> - pg_stat_reset()
> - pg_stat_reset_shared()
> - pg_stat_reset_single_table_counters()
> - pg_stat_reset_backend_stats()
> - pg_stat_reset_single_function_counters()
> - pg_stat_reset_slru()
> - pg_stat_reset_replication_slot()
> - pg_stat_reset_subscription_stats()
> - pg_stat_clear_snapshot()
>
> For pg_stat_reset_backend_stats() and
> pg_stat_reset_replication_slot(), the functions return the reset
> timestamp when a valid input is provided. If an invalid input is given
> (e.g., an invalid backend PID or replication slot name), the functions
> return NULL.
> This allows users to easily determine whether the reset operation was
> successful based on the return value.

I am not sure that this is a good idea overall, but I'm OK if I finish
outvoted.

At the exception of pg_stat_reset_backend_stats(), all the functions
you are listing above are written so as they never fail, so claiming
that returning a timestamp value for this reason sounds a bit strange
to me.  And we already know this information based on what the stats
tables already hold for the reset timestamps set when their stats
kinds callbacks are called.

I can get behind a change for pg_stat_reset_backend_stats() to make it
return a status, though, as the information depends on some procnum
lookups which is triggered depending on what the user provides in
input.
--
Michael