Re: Tsearch limitations

On Mon, 11 Aug 2003 psql-mail(at)freeuk(dot)com wrote:

> Oleg,
>
> I understand (i think) how the parser breaks up the input into words
> and builds ts_vector's.
>
> And i understand how to do queries as described into the documentation.
> (I have read it!)
>
> SELECT * FROM vectors WHERE vector @@ to_tsquery('(leads|forks) & !
> crawl')
>
> But i haven't seen any mention of if i add the word:
>
> cathedral
>
> if there is any query which will match if I search for "thed".

No, tsearch2 is a word oriented search. It doesn't supports substring
search.

>
> The documentation seems to say that this cannot be done - but i'd just
> like to check. Tsearch2 does everything i want except this.
>
> "remember that the search operator @@ finds only exact matches between
> query lexemes and vector lexemes ≈ if they are not exactly the same
> string, they will not be considered a match"
>
>
> > Mat,
> >
> > there are several function you may use to see (please, read
> documentation):
> >
> > apod=# select to_tsvector('Hi my email addres is psql-mail(at)freeuk(dot)com'
> );
> > to_tsvector
> > ----------------------------------------------------
> > 'hi':1 'addr':4 'email':3 'psql-mail(at)freeuk(dot)com':6
> > (1 row)
> >
> > or, even better
> >
> > apod=# select * from ts_debug('Hi my email addres is psql-mail(at)freeuk(dot)
> com');
> > ts_name | tok_type | description | token |
> dict_name | tsvector
> > -----------------+----------+-------------+----------------------+----
> -------+------------------------
> > default_russian | lword | Latin word | Hi | {
> en_stem} | 'hi'
> > default_russian | lword | Latin word | my | {
> en_stem} |
> > default_russian | lword | Latin word | email | {
> en_stem} | 'email'
> > default_russian | lword | Latin word | addres | {
> en_stem} | 'addr'
> > default_russian | lword | Latin word | is | {
> en_stem} |
> > default_russian | email | Email | psql-mail(at)freeuk(dot)com | {
> simple} | 'psql-mail(at)freeuk(dot)com'
> > (6 rows)
> >
> > You may write your own parser or preprocess text before tsearch.
> >
> > Oleg
> > On Mon, 11 Aug 2003, Mat wrote:
> >
> > > Can Tsearch be used to return substring matches?
> > >
> > > i.e
> > >
> > > Text to search: Hi my email addres is psql-mail(at)freeuk(dot)com
> > >
> > > Query "psql" would match the email address?
> > >
> > > Query "mail" would also match?
> > >
> > > Query "reeu" would also match?
> > >
> > > Or is tsearch not suitable for this type of query? should i use FTI
>
> > > instead?
> > >
> > > Thanks.
> > >
> > >
> > > ---------------------------(end of broadcast)-----------------------
> ----
> > > TIP 6: Have you searched our list archives?
> > >
> > > http://archives.postgresql.org
> > >
> >
> > Regards,
> > Oleg
> > _____________________________________________________________
> > Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> > Sternberg Astronomical Institute, Moscow University (Russia)
> > Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
> > phone: +007(095)939-16-83, +007(095)939-23-83
> >
>
>

Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83