Re: Query is over 2x slower with jit=on

Andres Freund <andres@anarazel.de>

From: Andres Freund <andres@anarazel.de>

To: Andreas Joseph Krogh <andreas@visena.com>

Cc: Robert Haas <robertmhaas@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, "Jonathan S. Katz" <jkatz@postgresql.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2018-08-22T18:52:05Z

Lists: pgsql-hackers

On 2018-08-22 19:51:12 +0200, Andreas Joseph Krogh wrote:
> I thought JITing of prepared queries happended once (in "prepare")

No, it happens when the first JITed function is executed.

>  so it didn't have to do the JITing every time the query is
> executed. Isn't the previously generated bytecode usable for
> subsequent queries?

No, not currently. There's some reasons preventing that (primarily that
we currently rely on addresses of certain things not to change during
execution). There's ongoing work to change that, but that's certainly
not going to be ready for v11.

Greetings,

Andres Freund

Commits

Fix issues around EXPLAIN with JIT.
- e97c4d967ba5 11.0 landed
- c03c1449c092 12.0 landed
Collect JIT instrumentation from workers.
- e63441c3f5ca 11.0 landed
- 33001fd7a707 12.0 landed
Make EXPLAIN output for JIT compilation more dense.
- 6859bd2632d8 11.0 landed
- 52050ad8ebec 12.0 landed
Save/restore SPI's global variables in SPI_connect() and SPI_finish().
- 825f10fbda7a 11.0 cited
Rationalize handling of single and double quotes in bootstrap data.
- 55d26ff638f0 11.0 cited