Hi, Oleg Bartunov:
First thanks for your quick replay. Could you explain it a little more on "it's
general limitation/feature"? I just confuse that to_tsquery('item') function
will return a tsquery type which is same as 'item'::tsquery, to my
understanding.
Let me explain what I want:First Step: extract top K tokensI have a table with
a column as tsvector type. Some records in this column are too big, which
contain hundreds tokens. I just want the top K tokens based on the frequency,
for example top 5. I am not sure there is a direct way to get such kind top K
tokens. I just read them out in Java and count frequency for each token and
sort them.
Second Step: generate queryNow I will use these tokens to construct a query to
search other vectors in the same table. I can not directly use to_tsquery() due
to two reasons: 1) The default logic operator in to_tsquery() is "&" but what I
need it "|". 2) Since the tokens are from tsvector, they are already
normalized. If I use to_tsquery() again, they will be normalized again! For
example, “course” -> “cours” -> “cour”. So I just concatenate the top K tokens
with “|” and directly use "::tsquery ".
Unfortunately, as you say "it's general limitation/feature”, I can not do that.
I checked your manual “Full-Text Search in PostgreSQL A Gentle Introduction”,
but could not figure out how. So is it possible to implement what I want in
FTS? If so, how?
Thank!
Xu
--- On Sun, 1/24/10, Oleg Bartunov <o...@sai.msu.su> wrote:
From: Oleg Bartunov <o...@sai.msu.su>
Subject: Re: [GENERAL] FTS uses "tsquery" directly in the query
To: "xu fei" <auto...@yahoo.com>
Cc: pgsql-general@postgresql.org
Date: Sunday, January 24, 2010, 2:11 AM
Xu,
FTS has nothing with your problem, it's general limitation/feature.
Oleg
On Sat, 23 Jan 2010, xu fei wrote:
> Hi, everyone:
> First I can successful run this query:select name, ts_rank_cd(vectors, query)
> as rank from element, to_tsquery('item') query where query @@ vectors order
> by rank desc;But actually I want to run this one:select name,
> ts_rank_cd(vectors, query) as rank from element, 'item'::tsquery query where
> query @@ vectors order by rank desc;Looks like that FTS does not support
> directly use "::tsquery " in such query. Do I misunderstand something?
> Thanks!
> Xu
>
>
>
Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: o...@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83
