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. James -----Original Message----- From: Tom Lane <tgl@xxxxxxxxxxxxx> Sent: Tuesday, June 21, 2022 10:30 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: > We have a large database that just migrated data from Oracle to Postgres(13.4), after data load. We try to create indexes , with only one connection , the create index automatically run in parallel (table size 40G) , then we started two connections and each session creating index on large table, but at this time, only 1 session parallel creating index, the other one creating index in serial. There are enough parallel_workers and memory. Is that expected ? only 1 session allowed to parallel index creating at the same time ? Check your settings for max_parallel_workers and max_parallel_maintenance_workers. regards, tom lane
