On Mon, Jun 13, 2016 at 5:27 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Mon, Jun 13, 2016 at 4:46 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Robert Haas <robertmh...@gmail.com> writes: >>> In practice, we don't yet have the ability for >>> parallel-safe paths from subqueries to affect planning at higher query >>> levels, but that's because the pathification stuff landed too late in >>> the cycle for me to fully react to it. >> >> I wonder if that's not just from confusion between subplans and >> subqueries. I don't believe any of the claims made in the comment >> adjusted in the patch below (other than "Subplans currently aren't passed >> to workers", which is true but irrelevant). Nested Gather nodes is >> something that you would need, and already have, a defense for anyway. > > I think you may be correct.
Oh, one other thing about this: I'm not going to try to defend whatever confusion between subplans and subqueries appears in that comment, but prior to upper planner pathification I think we were dead in the water here anyway, because the subquery was going to output a finished plan, not a list of paths. Since finished plans aren't labeled as to parallel-safety, we'd have to conservatively assume that the finished plan we got back might not be parallel-safe. Now that we're using the path representation throughout, we can do better. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
