Em qua., 20 de mai. de 2020 às 00:09, Thomas Munro <thomas.mu...@gmail.com> escreveu:
> On Wed, May 20, 2020 at 2:23 PM Amit Kapila <amit.kapil...@gmail.com> > wrote: > > Good experiment. IIRC, we have discussed a similar idea during the > > development of this feature but we haven't seen any better results by > > allocating in ranges on the systems we have tried. So, we want with > > the current approach which is more granular and seems to allow better > > parallelism. I feel we need to ensure that we don't regress > > parallelism in existing cases, otherwise, the idea sounds promising to > > me. > > Yeah, Linux seems to do pretty well at least with smallish numbers of > workers, and when you use large numbers you can probably tune your way > out of the problem. ZFS seems to do fine. I wonder how well the > other OSes cope. > Windows 10 (64bits, i5, 8GB, SSD) postgres=# set max_parallel_workers_per_gather = 0; SET Time: 2,537 ms postgres=# select count(*) from t; count ----------- 200000000 (1 row) Time: 47767,916 ms (00:47,768) postgres=# set max_parallel_workers_per_gather = 1; SET Time: 4,889 ms postgres=# select count(*) from t; count ----------- 200000000 (1 row) Time: 32645,448 ms (00:32,645) How display " -> execution time 5.2s, average read size ="? regards, Ranier VIlela
