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Thread: TSearch2 / Get all unique lexems

TSearch2 / Get all unique lexems

From
Hannes Dorbath
Date:
Is there a way to get all unique lexems from a table with a tsvector
column? The stat() function does this (and more), but I cannot use it..

Thanks


--
Regards,
Hannes Dorbath

Re: TSearch2 / Get all unique lexems

From
Oleg Bartunov
Date:
On Wed, 7 Dec 2005, Hannes Dorbath wrote:

> Is there a way to get all unique lexems from a table with a tsvector column?
> The stat() function does this (and more), but I cannot use it..

hmm, you could dump tsvector column and use awk+sort+uniq

>
> Thanks
>
>
>

     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

Re: TSearch2 / Get all unique lexems

From
Hannes Dorbath
Date:
On 07.12.2005 16:13, Oleg Bartunov wrote:
> hmm, you could dump tsvector column and use awk+sort+uniq

Thanks. I hoped for something possible inside a pl/pgsql proc. I'm
trying to integrate pg_trgm with Tsearch2. I'm still on my UTF-8
database. Yes I know, there is _NO_ UTF-8 support of any kind in
Tsearch2 yet, but I got it working to a degree that is OK for my
application (Created my own stemmer variant, ispell dict, affix file
etc). The last missing bit is to get a source for pg_trgm. I cannot use
the the stat() function, because it breaks as soon it sees an UTF-8 char.

I thought of using lexise(), cast the text array to rows somehow, write
it to a temp table, use SELECT DISTINCT.. but I hadn't any success yet.


--
Regards,
Hannes Dorbath

Re: TSearch2 / Get all unique lexems

From
Teodor Sigaev
Date:
> Thanks. I hoped for something possible inside a pl/pgsql proc. I'm
> trying to integrate pg_trgm with Tsearch2. I'm still on my UTF-8
> database. Yes I know, there is _NO_ UTF-8 support of any kind in
> Tsearch2 yet, but I got it working to a degree that is OK for my
> application (Created my own stemmer variant, ispell dict, affix file
> etc). The last missing bit is to get a source for pg_trgm. I cannot use
> the the stat() function, because it breaks as soon it sees an UTF-8 char.

I suppose noncompatible with UTF wordparser can produce illegal lexemes (with
part of multibyte char) and stores it in tsvector. Tsvector hasn't any control
of breakness lexemes (with a help pg_verifymbstr() call), but stat() makes text
field and then postgres check it and found incomplete mbchars. Which way I see
(except waiting UTF support in tsearch2 which we develop now):

1 modify stat() function to check text field and if it fails then remove lexeme
from output

2 Take from CVS HEAD wordpaser (ts_locale.[ch], wparser_def.c,
wordparser/parser.[ch]). to_tsvector will works fine, to_tsquery will works
correct only with quoted string  (for examle, 'foo' & 'bar',  bad: foo & bar).
But casting 'asasas'::tsvector and dump/reload will not work correct.




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

Re: TSearch2 / Get all unique lexems

From
Oleg Bartunov
Date:
On Thu, 8 Dec 2005, Hannes Dorbath wrote:

> On 07.12.2005 16:13, Oleg Bartunov wrote:
>> hmm, you could dump tsvector column and use awk+sort+uniq
>
> Thanks. I hoped for something possible inside a pl/pgsql proc. I'm trying to
> integrate pg_trgm with Tsearch2. I'm still on my UTF-8 database. Yes I know,
> there is _NO_ UTF-8 support of any kind in Tsearch2 yet, but I got it working
> to a degree that is OK for my application (Created my own stemmer variant,
> ispell dict, affix file etc). The last missing bit is to get a source for
> pg_trgm. I cannot use the the stat() function, because it breaks as soon it
> sees an UTF-8 char.

unless there is some way to ignore errors in utf8 convertation to text
this is a dead-end. stat() function uses text representation.

You have to wait new release with full UTF8 support or go 'lazy' way,
i.e. use any tools to get a list of unique words and create pg_trgm index.
There are several questions:
* Do you actually need to be synchronized with tsvector ?
* Do you need to recognize all words ? I supposed no. In real life you should
have a dictionary which you certainly need to recognize.


     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