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Re: Parallel execution and prepared statements

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tobias Bussmann <t.bussmann@gmx.net>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Albe Laurenz <laurenz.albe@wien.gv.at>
Date: 2016-11-16T15:35:37Z
Lists: pgsql-hackers

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  1. Enable parallelism for prepared statements and extended query protocol.

On Tue, Nov 15, 2016 at 3:57 PM, Tobias Bussmann <t.bussmann@gmx.net> wrote:
> As the patch in [1] targeting the execution of the plan in ExecutePlan depending on the destination was declined, I hacked around a bit to find another way to use parallel mode with SQL prepared statements while disabling the parallel execution in case of an non read-only execution. For this I used the already present test for an existing intoClause in ExecuteQuery to set the parallelModeNeeded flag of the prepared statement. This results in a non parallel execution of the parallel plan, as we see with a non-zero fetch count used with the extended query protocol. Despite this patch seem to work in my tests, I'm by no means confident this being a proper way of handling the situation in question.

Yeah, we could do something like this, perhaps not in exactly this
way, but I'm not sure it's a good idea to just execute the parallel
plan without workers.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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