| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Jeff Davis <jdavis(at)postgresql(dot)org> |
| Subject: | Re: pg13dev: explain partial, parallel hashagg, and memory use |
| Date: | 2020-08-05 02:27:26 |
| Message-ID: | CAApHDvo_rw8tix0PPRUTaaAjfm9uU_WHfmRy=4X3eSSpSqr5FA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 5 Aug 2020 at 14:13, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> Also odd (to me). If I encourage more workers, there are "slots" for each
> "planned" worker, even though fewer were launched:
Looking at explain.c for "num_workers; " (including the final space at
the end), looking at each for loop that loops over each worker, quite
a number of those locations have a condition that skips the worker.
For example, show_sort_info() does
if (sinstrument->sortMethod == SORT_TYPE_STILL_IN_PROGRESS)
continue; /* ignore any unfilled slots */
So maybe Hash Agg should be doing something similar. Additionally,
maybe it should not show the leader details if the leader didn't help.
David
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