Re: Parallel Seq Scan

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel Seq Scan
Date: 2015-01-11 03:40:58
Message-ID: CA+Tgmoa_oVw5FUJoyE_7C5UudKiSL92ZkXpjVzU37wqLANxzKA@mail.gmail.com
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On Thu, Jan 8, 2015 at 2:46 PM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> Yeah, if we come up with a plan for X workers and end up not being able
> to spawn that many then I could see that being worth a warning or notice
> or something. Not sure what EXPLAIN has to do anything with it..

That seems mighty odd to me. If there are 8 background worker
processes available, and you allow each session to use at most 4, then
when there are >2 sessions trying to do parallelism at the same time,
they might not all get their workers. Emitting a notice for that
seems like it would be awfully chatty.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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