Hi, On Wed, Jul 17, 2019 at 11:58 PM Tom Lane <t...@sss.pgh.pa.us> wrote:
> =?UTF-8?Q?Darafei_=22Kom=D1=8Fpa=22_Praliaskouski?= <m...@komzpa.net> > writes: > > Many thanks for the parallel improvements in Postgres 12. Here is one of > > cases where a costy function gets moved from a parallel worker into main > > one, rendering spatial processing single core once again on some queries. > > Perhaps an assumption "expressions should be mashed together as much as > > possible" should be reviewed and something along "biggest part of > > expression should be pushed down into parallel worker"? > > I don't see anything in your test case that proves what you think it does. > The expensive calculation *is* being done in the worker in the first > example. It's not real clear to me why the first example is only choosing > to use one worker rather than 3, but probably with a larger test case > (ie bigger table) that decision would change. > Indeed, it seems I failed to minimize my example. Here is the actual one, on 90GB table with 16M rows: https://gist.github.com/Komzpa/8d5b9008ad60f9ccc62423c256e78b4c I can share the table on request if needed, but hope that plan may be enough. -- Darafei Praliaskouski Support me: http://patreon.com/komzpa
