Robert Haas <robertmh...@gmail.com> writes: > On Fri, Oct 21, 2011 at 10:57 PM, Jeff Janes <jeff.ja...@gmail.com> wrote: >> If count(*) could cause the index-only scan to happen in physical >> order of the index, rather than logical order, that might be a big >> win. Both for all in memory and for not-all-in-memory.
> That's an interesting point. I sort of assumed that would only help > for not-all-in-memory, but maybe not. The trouble is that I think > there are some problematic concurrency issues there. Yeah. We managed to make physical-order scanning work for VACUUM because it's okay if VACUUM sometimes sees the same index tuple twice; it'll just make the same decision about (not) deleting it. That will not fly for regular querying. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers