On Mon, Mar 14, 2016 at 3:56 PM, Paul Ramsey <pram...@cleverelephant.ca> wrote: > On Sun, Mar 13, 2016 at 7:31 PM, David Rowley > <david.row...@2ndquadrant.com> wrote: >> On 14 March 2016 at 14:52, James Sewell <james.sew...@lisasoft.com> wrote: >>> One question - how is the upper limit of workers chosen? >> >> See create_parallel_paths() in allpaths.c. Basically the bigger the >> relation (in pages) the more workers will be allocated, up until >> max_parallel_degree. > > Does the cost of the aggregate function come into this calculation at > all? In PostGIS land, much smaller numbers of rows can generate loads > that would be effective to parallelize (worker time much >> than > startup cost).
Unfortunately, no - only the table size. This is a problem, and needs to be fixed. However, it's probably not going to get fixed for 9.6. :-( -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers