On Thu, Dec 11, 2014 at 2:51 PM, Tomas Vondra <t...@fuzzy.cz> wrote: > No, it's not rescanned. It's scanned only once (for the batch #0), and > tuples belonging to the other batches are stored in files. If the number > of batches needs to be increased (e.g. because of incorrect estimate of > the inner table), the tuples are moved later.
Yeah, I think I sort of knew that, but I got confused. Thanks for clarifying. > The idea was that if we could increase the load a bit (e.g. using 2 > tuples per bucket instead of 1), we will still use a single batch in > some cases (when we miss the work_mem threshold by just a bit). The > lookups will be slower, but we'll save the I/O. Yeah. That seems like a valid theory, but your test results so far seem to indicate that it's not working out like that - which I find quite surprising, but, I mean, it is what it is, right? -- 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
