On Wed, Jan 28, 2015 at 10:40 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> The problem here, as I see it, is that we're flying blind. If there's >> just one spindle, I think it's got to be right to read the relation >> sequentially. But if there are multiple spindles, it might not be, >> but it seems hard to predict what we should do. We don't know what >> the RAID chunk size is or how many spindles there are, so any guess as >> to how to chunk up the relation and divide up the work between workers >> is just a shot in the dark. > > I thought the proposal to chunk on the basis of "each worker processes > one 1GB-sized segment" should work all right. The kernel should see that > as sequential reads of different files, issued by different processes; > and if it can't figure out how to process that efficiently then it's a > very sad excuse for a kernel.
I agree. But there's only value in doing something like that if we have evidence that it improves anything. Such evidence is presently a bit thin on the ground. -- 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
