Re: ts_headline

As it turns out, all I needed was in the doco but the key element - the first
config arg to ts_headline - was not in any of the examples so I missed it.

Would it be possible for ts_headline to work with the pre-parsed ts_vector?

I see references to future plans for phrase searching in ts. Is there a date
for this?

Cheers and thanks,
Stephen
Davies

On Friday 22 February 2008 22:54, Oleg Bartunov wrote:
> On Fri, 22 Feb 2008, Stephen Davies wrote:
> > Hmmmm!
> > I think I now understand the ts position better, thank you.
> >
> > Part of my problem has been that I am used to the functionality of Open
> > Text's LCS (aka BASIS) product which handles text differently.
> >
> > It includes the position (and context) information in the index and does
> > "remember" how the text was parsed so does not need to reparse to insert
> > hit navigation tags nor need pointers as to how to parse queries. (It
> > also supports phrase searching.)
> >
> > Now that I have a better understanding of ts, I think I will be able to
> > make it do at least most of what I hoped for.
>
> I'm wondering if it was not described in the text search documentation :)
>
> > Thank you again for your help with this.
> >
> > Cheers,
> > Stephen Davies
> >
> > On Friday 22 February 2008 20:45, Richard Huxton wrote:
> >> Stephen Davies wrote:
> >>> Unfortunately, my link to the box with the test database is down due to
> >>> lack of maintenance by our local telco (Telstra) but I think that I
> >>> also missed the optional config arg to ts_headline.
> >>>
> >>> The lack of link also means that I cannot confirm your findings but
> >>> your logic looks good.
> >>
> >> Looks like ALTER DATABASE SET default_text_config='english' is what you
> >> need.
> >>
> >>> It begs the question, however, as to why ts-headline needs to reparse
> >>> the raw text.
> >>
> >> It needs to line up tsvector lexemes with actual characters in the text.
> >> The tsvector is missing punctuation, any stopwords (the, it, a) as well
> >> as being stemmed (if your dictionary does that).
> >>
> >> Also, it's looking for a short span of words that provide the best
> >> match. That might not be a complete match of course, and is different to
> >> how you'd normally look to use a tsvector.
> >>
> >>> At least in my case, I am using a trigger to parse the combination of
> >>> Title and Abstract to a ts_vector field in the table row (as suggested
> >>> in 12.2.2 and 12.4.3 in the doco) so that the ts_vector is already
> >>> available to ts_headline.
> >>>
> >>> If ts_headline had the ability to use that pre-parsed ts_vector, my
> >>> problem would never have arisen - and the performance of ts_headline
> >>> would be improved.
> >>
> >> Maybe. It would still have to parse the text to some degree though, just
> >> to get the original words & punctuation into the headline.
>
> Regards,
> Oleg
> _____________________________________________________________
> Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
> Sternberg Astronomical Institute, Moscow University, Russia
> Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
> phone: +007(495)939-16-83, +007(495)939-23-83

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