Обсуждение: multi-word expression full-text searching

Hello all:

I'm testing all full-text searching possibilities of PostgreSQL and...

Is it possible to search for a multi-word expression?

I can search one or more words:

SELECT id FROM document WHERE to_tsvector('english',text) @@
to_tsquery('english','despite');

SELECT id FROM document WHERE to_tsvector('english',text) @@
to_tsquery('english','despite & subject');

But it seems not be possible to do a query like:

SELECT id FROM document WHERE to_tsvector('english',text) @@
to_tsquery('english','despite this');

to search the documents in which occur the expression "despite this".
This last query gives the following error:

ERROR:  syntax error in tsquery: "despite this"

Is it really impossible to searh a multi-word expression?

Thanks in advance,

  Mario Barcala

SELECT id FROM document WHERE to_tsvector('english',text) @@
plainto_tsquery('english','despite this');
--
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                    WWW: http://www.sigaev.ru/

>
> SELECT id FROM document WHERE to_tsvector('english',text) @@
> plainto_tsquery('english','despite this');
> --
> Teodor Sigaev

If I understand well the plainto_tsquery behaviour, this query match with:

Despite this, the president went out.
Despite the event, this question arise.

i.e., if "this" is not inside the stopwords list, the query is translated to:
SELECT id FROM document WHERE to_tsvector('english',text) @@
to_tsquery('english','despite & this');

It searches for documents which include "despite" and "this", and not for
ones which have the expression "despite this".

I have made some tests and they confirm my explanations.

Thank you anyway.

Any other solution?

Mario Barcala

On Tue, 1 Jul 2008, lbarcala@freeresearch.org wrote:

>>
>> SELECT id FROM document WHERE to_tsvector('english',text) @@
>> plainto_tsquery('english','despite this');
>> --
>> Teodor Sigaev
>
> If I understand well the plainto_tsquery behaviour, this query match with:
>
> Despite this, the president went out.
> Despite the event, this question arise.

You want 'phrase search', which doesn't supported yet. There are
several workarounds, search archives for 'phrase search'

>
> i.e., if "this" is not inside the stopwords list, the query is translated to:
> SELECT id FROM document WHERE to_tsvector('english',text) @@
> to_tsquery('english','despite & this');
>
> It searches for documents which include "despite" and "this", and not for
> ones which have the expression "despite this".
>
> I have made some tests and they confirm my explanations.
>
> Thank you anyway.
>
> Any other solution?
>
> Mario Barcala
>
>
>
>
>
>

     Regards,
         Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83

> If I understand well the plainto_tsquery behaviour, this query match with:
> Despite this, the president went out.
> Despite the event, this question arise.

Right, you mean phrase search. Read the thread:
http://archives.postgresql.org/pgsql-hackers/2008-05/msg01111.php

Suggested patch should be made as module, I think.



--
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                    WWW: http://www.sigaev.ru/