Parallel execution and prepared statements

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

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

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

Cc: "'t.bussmann@gmx.net'" <t.bussmann@gmx.net>

Date: 2016-11-15T15:41:18Z

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

0001-Consider-parallel-plans-for-statements-prepared-with.patch (application/octet-stream) patch 0001

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.

Yours,
Laurenz Albe