On Tue, Jul 23, 2013 at 2:24 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Tue, Jul 23, 2013 at 12:28 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> As far as get_actual_variable_range() is concerned, an MVCC snapshot >>> would probably be the thing to use anyway; > >> That surprises me, though. I really thought the point was to cost the >> index scan, and surely that will be slowed down even by entries we >> can't see. > > No, the usage (or the main usage anyway) is for selectivity estimation, > ie how many rows will the query fetch.
OK, so GetActiveSnapshot()? -- 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
