Re: Introduce a new view for checkpointer related stats

Hi,

On 2022-11-22 18:08:28 +0530, Bharath Rupireddy wrote:
> diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
> index 2d8104b090..131d949dfb 100644
> --- a/src/backend/catalog/system_views.sql
> +++ b/src/backend/catalog/system_views.sql
> @@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
>  
>  CREATE VIEW pg_stat_bgwriter AS
>      SELECT
> -        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
> -        pg_stat_get_bgwriter_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_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
>          pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
>          pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
> -        pg_stat_get_buf_written_backend() AS buffers_backend,
> -        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
>          pg_stat_get_buf_alloc() AS buffers_alloc,
>          pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
>  
> +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 think we should consider deprecating the pg_stat_bgwriter columns but
leaving them in place for a few years. New stuff should only be added to
pg_stat_checkpointer, but we don't need to break old monitoring queries.

Greetings,

Andres Freund