Re: Parallel workers stats in pg_stat_database

Hi,

Thanks for your imput ! I will fix the doc as proposed and do the split 
as soon as I have time.

On 10/1/24 09:27, Michael Paquier wrote:
> I'm less
> a fan of the addition for utilities because these are less common
> operations.

My thought process was that in order to size max_parallel_workers we 
need to
have information on the maintenance parallel worker and "query" parallel 
workers.

> Actually, could we do better than what's proposed here?  How about
> presenting an aggregate of this data in pg_stat_statements for each
> query instead?

I think both features are useful.

My collegues and I had a discussion about what could be done to improve
parallelism observability in PostgreSQL [0]. We thought about several
places to do it for several use cases.

Guillaume Lelarge worked on pg_stat_statements [1] and
pg_stat_user_[tables|indexes] [2]. I proposed a patch for the logs [3].

As a consultant, I frequently work on installation without
pg_stat_statements and I cannot install it on the client's production
in the timeframe of my intervention.

pg_stat_database is available everywhere and can easily be sampled by 
collectors/supervision services (like check_pgactivity).

Lastly the number would be more precise/easier to make sense of, since 
pg_stat_statement has a limited size.

[0] 
https://www.postgresql.org/message-id/flat/d657df20-c4bf-63f6-e74c-cb85a81d0383@dalibo.com
[1] 
https://www.postgresql.org/message-id/CAECtzeWtTGOK0UgKXdDGpfTVSa5bd_VbUt6K6xn8P7X%2B_dZqKw%40mail.gmail.com
[2] 
https://www.postgresql.org/message-id/flat/CAECtzeXXuMkw-RVGTWvHGOJsmFdsRY%2BjK0ndQa80sw46y2uvVQ%40mail.gmail.com
[3] 
https://www.postgresql.org/message-id/8123423a-f041-4f4c-a771-bfd96ab235b0%40dalibo.com

-- 
Benoit Lobréau
Consultant
http://dalibo.com