On Mon, Oct 22, 2012 at 11:57 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Pavel Stehule <pavel.steh...@gmail.com> writes: >> but using DISTINCT breaks KNN searching optimization > >> postgres=# explain select distinct nazobce, nazobce <-> 'Benešov' from >> obce order by nazobce <-> 'Benešov' limit 10 > > Don't hold your breath. There are two ways the system could implement > the DISTINCT clause: either sort and uniq, or hashaggregate. > hashaggregate will destroy any input ordering, so there's no value in > using the index as input.
Isn't that an implementation limitation though, rather than a fundamental limitation? -- 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
