On Mon, Jun 13, 2016 at 1:06 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Mon, Jun 13, 2016 at 11:02 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> BTW, decent regression tests could be written without the need to create >>> enormous tables if the minimum rel size in create_plain_partial_paths() >>> could be configured to something less than 1000 blocks. I think it's >>> fairly crazy that that arbitrary constant is hard-wired anyway. Should >>> we make it a GUC? > >> That was proposed before, and I didn't do it mostly because I couldn't >> think of a name for it that didn't sound unbelievably corny. > > min_parallel_relation_size, or min_parallelizable_relation_size, or > something like that?
Sure. >> Also, >> the whole way that algorithm works is kind of a hack and probably >> needs to be overhauled entirely in some future release. I'm worried >> about having the words "backward compatibility" thrown in my face when >> it's time to improve this logic. But aside from those two issues I'm >> OK with exposing a knob. > > I agree it's a hack, and I don't want to expose anything about the > number-of-workers scaling behavior, for precisely that reason. But a > threshold on the size of a table to consider parallel scans for at all > doesn't seem unreasonable. OK. -- 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