Em qua., 1 de fev. de 2023 às 02:39, Alex Kaiser <alextkai...@gmail.com> escreveu:
> Hello, > > I'm trying to get the following query to use a plan with parallelism, but > I haven't been successful and would like some advice. > > The schema and table that I'm using is this: > > CREATE TABLE testing( > id INT, > info INT, > data_one TEXT, > data_two TEXT, > primary key(id, info) > ); > > INSERT INTO testing(id, info, data_one, data_two) > SELECT idx, idx, md5(random()::text), md5(random()::text) > FROM generate_series(1,10000000) idx; > > Then the query that I'm trying to run is this (I'll include the full query > at the very end of the email because it is long: > > select * from testing where id in (1608377,5449811, ... <1000 random ids> > ,4654284,3558460); > > Essentially I have a list of 1000 ids and I would like the rows for all of > those ids. > > This seems like it would be pretty easy to parallelize, if you have X > threads then you would split the list of IDs into 1000/X sub lists and give > one to each thread to go find the rows for ids in the given list. Even > when I use the following configs I don't get a query plan that actually > uses any parallelism: > > psql (15.1 (Debian 15.1-1.pgdg110+1)) > Type "help" for help. > > postgres=# show max_parallel_workers; > max_parallel_workers > ---------------------- > 8 > (1 row) > > postgres=# set max_parallel_workers_per_gather = 8; > SET > postgres=# set parallel_setup_cost = 0; > SET > postgres=# set parallel_tuple_cost = 0; > SET > postgres=# set force_parallel_mode = on; > SET > postgres=# explain select * from testing where id in (1608377,5449811, ... > <removed for brevity> ... ,4654284,3558460); > Can you try: select * from testing where id any = (values(1608377),(5449811),(5334677) ... <removed for brevity> ... ,(4654284),(3558460)); Or alternately you can use EXTEND STATISTICS to improve Postgres planner choice. regards, Ranier Vilela
