Horton

Re: Parallel execution and prepared statements

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Albe Laurenz <laurenz.albe@wien.gv.at>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "t.bussmann@gmx.net" <t.bussmann@gmx.net>
Date: 2016-11-16T13:47:16Z
Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

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

On Tue, Nov 15, 2016 at 10:41 AM, Albe Laurenz <laurenz.albe@wien.gv.at> wrote:
> Tobias Bussmann has discovered an oddity with prepared statements.
>
> Parallel scan is used with prepared statements, but only if they have
> been created with protocol V3 "Parse".
> If a prepared statement has been prepared with the SQL statement PREPARE,
> it will never use a parallel scan.
>
> I guess that is an oversight in commit 57a6a72b, right?
> PrepareQuery in commands/prepare.c should call CompleteCachedPlan
> with cursor options CURSOR_OPT_PARALLEL_OK, just like
> exec_prepare_message in tcop/postgres.c does.
>
> The attached patch fixes the problem for me.

Actually, commit 57a6a72b made this change, and then 7bea19d0 backed
it out again because it turned out to break things.

-- 
Robert Haas
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