Re: Parallel execution and prepared statements

Tobias Bussmann <t.bussmann@gmx.net>

From: Tobias Bussmann <t.bussmann@gmx.net>

To: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>

Cc: Albe Laurenz <laurenz.albe@wien.gv.at>

Date: 2016-11-15T20:57:09Z

Lists: pgsql-hackers

Commits

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

Enable parallelism for prepared statements and extended query protocol.
- 57a6a72b6bc9 9.6.0 cited

Attachments

prepared_stmt_execute_parallel_query.patch (application/octet-stream) patch
(unnamed) (text/plain)

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.

Best 
Tobias 

[1] https://www.postgresql.org/message-id/CAA4eK1KxiYm8F9Pe9xvqzoZocK43w%3DTRPUNHZpe_iOjF%3Dr%2B_Vw%40mail.gmail.com