On 2017-06-06 23:32:53 -0400, Peter Eisentraut wrote: > On 6/6/17 13:52, Regina Obe wrote: > > It seems CREATE AGGREGATE was expanded in 9.6 to support parallelization of > > aggregate functions using transitions, with the addition of serialfunc and > > deserialfunc to the aggregate definitions. > > > > https://www.postgresql.org/docs/10/static/sql-createaggregate.html > > > > I was looking at the PostgreSQL 10 source code for some example usages of > > this and was hoping that array_agg and string_agg would support the feature. > > I'm not sure how you would parallelize these, since in most uses you > want to have a deterministic output order.
Unless you specify ORDER BY you don't really have that anyway, consider hash-aggregation. If you want deterministic order, you really need an ORDER BY inside the aggregate. - Andres -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers