Re: [HACKERS] pg_stat_wal_write statistics view

On Tue, Feb 7, 2017 at 11:47 AM, Haribabu Kommi
<kommi.haribabu@gmail.com> wrote:
> Hi Hackers,
>
> I just want to discuss adding of a new statistics view that provides
> the information of wal writing details as follows
>

+1.  I think it will be useful to observe WAL activity.

> postgres=# \d pg_stat_wal_writer
>                         View "pg_catalog.pg_stat_wal_writer"
>         Column         |           Type           | Collation | Nullable |
> Default
> -----------------------+--------------------------+-----------+----------+---------
>  num_backend_writes       | bigint                   |           |
> |
>  num_total_writes  | bigint                   |           |          |
>  num_blocks  | bigint                   |           |          |
>  total_write_time   | bigint|           |          |
>  stats_reset           | timestamp with time zone |           |          |
>
> The columns of the view are
> 1. Total number of xlog writes that are called from the backend.
> 2. Total number of xlog writes that are called from both backend
>  and background workers. (This column can be changed to just
>  display on the background writes).
> 3. The number of the blocks that are written.
> 4. Total write_time of the IO operation it took, this variable data is
> filled only when the track_io_timing GUC is enabled.

So, here is *write_time* the total time system has spent in WAL
writing before the last reset?

I think there should be a separate column for write and sync time.

> Or it is possible to integrate the new columns into the existing
> pg_stat_bgwriter view also.
>

I feel separate view is better.