Re: how does PostgreSQL determine how many parallel processes to start - Mailing list pgsql-general

From Luca Ferrari
Subject Re: how does PostgreSQL determine how many parallel processes to start
Date
Msg-id CAKoxK+75LgN40TBUNTBgWYfr8SYFNvPUJqe0cgDggzGUBw92fQ@mail.gmail.com
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In response to Re: how does PostgreSQL determine how many parallel processes to start  (Laurenz Albe <laurenz.albe@cybertec.at>)
Responses Re: how does PostgreSQL determine how many parallel processes to start
List pgsql-general
On Fri, Feb 19, 2021 at 10:43 AM Laurenz Albe <laurenz.albe@cybertec.at> wrote:
> At execution time, PostgreSQL will use as many of the planned workers
> as are currently available (max_parallel_workers).

Thanks, but just to make it clear, assuming I execute almost
simultanously two identical queries that can be therefore be
parallelized, does that mean that the first one will be executed with
the max available parallele capacity and the second will "starve" on
parllelism being executed sequentially. Is this correct?
As a consequence to that, this also could mean that a query over a
small table could take more advanatge (in parallel sense) than a scan
on a larger table that was issued just a moment after (assuming both
table can be scanned in parallel), right?

Luca



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