Is there any way to sort by ranking, avoiding seq scan? The only way i see now is to use pg_trgm instead of ts_rank, but we did not check yet how applicable is it for our purposes. 7 марта 2012 г. 20:53 пользователь Nicolas Grilly <nicolas@xxxxxxxxxxxxxxxx> написал: > 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 <andll@xxxxxxxxxxx> 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@xxxxxxxxxxxxxx) >> 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 -- Regards, Andrey -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
