| From: | Vijaykumar Jain <vijaykumarjain(dot)github(at)gmail(dot)com> |
|---|---|
| To: | "ldh(at)laurent-hasson(dot)com" <ldh(at)laurent-hasson(dot)com> |
| Cc: | Justin Pryzby <pryzby(at)telsasoft(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Big performance slowdown from 11.2 to 13.3 |
| Date: | 2021-07-22 20:31:45 |
| Message-ID: | CAM+6J96WbdrdwyhSJG4timezpjJ=9cO+qEE7Gr9Jtyr58XN7SQ@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-performance |
Just asking, I may be completely wrong.
is this query parallel safe?
can we force parallel workers, by setting low parallel_setup_cost or
otherwise to make use of scatter gather and Partial HashAggregate(s)?
I am just assuming more workers doing things in parallel, would require
less disk spill per hash aggregate (or partial hash aggregate ?) and the
scatter gather at the end.
I did some runs in my demo environment, not with the same query, some group
by aggregates with around 25M rows, and it showed reasonable results, not
too off.
this was pg14 on ubuntu.
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| Previous Message | Alvaro Herrera | 2021-07-22 17:56:54 | Re: Big performance slowdown from 11.2 to 13.3 |