Re: Introduce a new view for checkpointer related stats

On Wed, Nov 30, 2022 at 12:44 PM Drouvot, Bertrand
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> +CREATE VIEW pg_stat_checkpointer AS
> + SELECT
> + pg_stat_get_timed_checkpoints() AS checkpoints_timed,
> + pg_stat_get_requested_checkpoints() AS checkpoints_req,
> + pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
> + pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
> + pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
> + pg_stat_get_buf_written_backend() AS buffers_backend,
> + pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
> + pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
> +
>
> I still think that having checkpoints_ prefix in a pg_stat_checkpointer view sounds "weird" (made sense when they were part of pg_stat_bgwriter)
>
> maybe we could have something like this instead?
>
> +CREATE VIEW pg_stat_checkpointer AS
> + SELECT
> + pg_stat_get_timed_checkpoints() AS num_timed,
> + pg_stat_get_requested_checkpoints() AS num_req,
> + pg_stat_get_checkpoint_write_time() AS total_write_time,
> + pg_stat_get_checkpoint_sync_time() AS total_sync_time,
> + pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
> + pg_stat_get_buf_written_backend() AS buffers_backend,
> + pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
> + pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
> +

I don't have a strong opinion about changing column names. However, if
we were to change it, I prefer to use names that
PgStat_CheckpointerStats has. BTW, that's what
PgStat_BgWriterStats/pg_stat_bgwriter and
PgStat_ArchiverStats/pg_stat_archiver uses.
typedef struct PgStat_CheckpointerStats
{
PgStat_Counter timed_checkpoints;
PgStat_Counter requested_checkpoints;
PgStat_Counter checkpoint_write_time; /* times in milliseconds */
PgStat_Counter checkpoint_sync_time;
PgStat_Counter buf_written_checkpoints;
PgStat_Counter buf_written_backend;
PgStat_Counter buf_fsync_backend;
TimestampTz stat_reset_timestamp;
} PgStat_CheckpointerStats;

> That's a nit in any case and the patch LGTM.

Thanks.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com