On 2015-04-21 AM 03:29, Robert Haas wrote: > On Wed, Apr 8, 2015 at 3:38 AM, Amit Langote wrote: >> On 08-04-2015 PM 12:46, Amit Kapila wrote: >>> Going forward, I think we can improve the same if we decide not to shutdown >>> parallel workers till postmaster shutdown once they are started and >>> then just allocate them during executor-start phase. >> >> I wonder if it makes sense to invent the notion of a global pool of workers >> with configurable number of workers that are created at postmaster start and >> destroyed at shutdown and requested for use when a query uses parallelizable >> nodes. > > Short answer: Yes, but not for the first version of this feature. > > Longer answer: We can't actually very reasonably have a "global" pool > of workers so long as we retain the restriction that a backend > connected to one database cannot subsequently disconnect from it and > connect to some other database instead. However, it's certainly a > good idea to reuse the same workers for subsequent operations on the > same database, especially if they are also by the same user. At the > very minimum, it would be good to reuse the same workers for > subsequent operations within the same query, instead of destroying the > old ones and creating new ones. Notwithstanding the obvious value of > all of these ideas, I don't think we should do any of them for the > first version of this feature. This is too big a thing to get perfect > on the first try. >
Agreed. Perhaps, Amit has worked (is working) on "reuse the same workers for subsequent operations within the same query" Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
