Sorry for confusion. This time, I add "max_parallel_workers"=32 , "max_parallel_maintenance_workers"=32 , "max_workers_process"=64 to postgresql.conf, and restart database. This time, both session runs in parallel now. Last several tests only got these parameter changes by set max_parallell_workers... in session level , for each session , only 1 session parallel creating index. James -----Original Message----- From: James Pang (chaolpan) Sent: Wednesday, June 22, 2022 9:34 AM To: Tom Lane <tgl@xxxxxxxxxxxxx> Cc: pgsql-admin@xxxxxxxxxxxxxxxxxxxx Subject: RE: multiple sessions to create index in parallel support All max_workers_process got increased to 32 before creating index. The 2 session try to create index on totally separate large tables(40gb) , either one in 8 parallel workers, but not both. James -----Original Message----- From: Tom Lane <tgl@xxxxxxxxxxxxx> Sent: Tuesday, June 21, 2022 11:04 PM To: James Pang (chaolpan) <chaolpan@xxxxxxxxx> Cc: pgsql-admin@xxxxxxxxxxxxxxxxxxxx Subject: Re: multiple sessions to create index in parallel support "James Pang (chaolpan)" <chaolpan@xxxxxxxxx> writes: > Max_parallel_workers and max_parallel_maintenance_workers both equal to 32, one session create one index in a large table show parallel 8 workers, the other session creating one index in another separate table always in serial. Even increase max_parallel_worers and max_parallel_maintenance_workers to 64, still show one is parallel 8 workers, the other is done in serial. Hmm, what about max_worker_processes ? That's an independent limit. regards, tom lane
