Re: Logging parallel worker draught

On 4/7/25 6:41 PM, Melanie Plageman wrote:
> On Mon, Feb 3, 2025 at 12:37 AM Sami Imseih <samimseih(at)gmail(dot)com> wrote:
> I started looking at this, and I like the idea.

Thanks for taking a look!

> A few comments: I don't understand what 0002 is. For starters, the
> commit message says something about pg_stat_database, and there are no
> changes related to that.

I had originally split this part out while working on the patch to add
parallel worker stats in pg_stat_database [1], in order to isolate the
common components. In the end, that patch only accounted for user queries.

I merged it into "Implements logging for parallel worker usage in
utilities" for v9.

> Also, we already have basically identical logging coming from
> parallel_vacuum_process_all_indexes() and viewable in existing output.
> Not only does your implementation not replace this, it is odd that
> setting your new guc to none does not disable this. It seems a bit
> inconsistent. I'm not sure what the exact right behavior is here,
> though.

That logging is used for the VERBOSE mode of VACUUM. There was also
dicussion to add similar info for parallel index creation.

The use case here is different — the goal is to audit parallel worker
usage across the entire instance, without needing every call site to use
VACUUM (VERBOSE) along with SET log_min_messages = info.

I avoided reusing that part of the code because I thought the
expectation was to aggregate worker counts and display them in
parallel_vacuum_end(). Sami also mentionned that using the same log
line everywhere in the patch would make parsing easier, which I tought
was a good idea.

> Since your last update, it seems parallel gin index build has been
> committed, so perhaps you want to add that.

Thanks for the heads-up! I've added logging in _gin_end_parallel().

You’ll find the updated patch attached.

[1] https://commitfest.postgresql.org/patch/5212/

--
Benoit