According to Oleg in a previous discussion, ts_rank does not use index because index does not store enough information for ranking: http://archives.postgresql.org/pgsql-general/2011-07/msg00351.php
On Sat, Feb 18, 2012 at 12:39, Andrey Chursin <an...@danasoft.ws> wrote: > Hello > > I have two unrelated questions about fts function ts_rank: > > 1) I've created GiST index on column with fts vector, but query > SELECT * FROM table ORDER BY ts_rank(field, :query) LIMIT 20 > is perfomed with sequential table scan. Index was created on field > column. Does it mean FTS indexes does not support order by ranking? Or > I need somehow to create separated index for ranking? > > 2) I have a misunderstanding with proximity ranking work. Given two > vectors 'a:1 b:2' and 'a:1 b:1000', i am measuring ts_rank(vector, 'a' > | 'b'). And it is equal! But when i am replacing query with & > operator, e.g. asking for ts_rank(vector, 'a' & 'b') i am getting > different numbers. Why do I get proximity ranking only for AND fts > queries? This is a problem as far as to_tsquery produces OR queries, > so i need self-written postprocessing of query to replace OR with AND. > > -- > Regards, > Andrey > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > -- Nicolas Grilly Garden / Vocation City +33 1 45 72 48 78 - office +33 6 03 00 25 34 - mobile www.gardentechno.com - Développement web & reporting / *Web development & data analytics* www.vocationcity.com - Plateforme de recrutement sur le web / *Web recruitment platform*
