Re: ts_rank

Oleg Bartunov wrote:
> I'm sorry, my plane to Nepal is waiting me :) I'll be back in the
> midst of November. In short, ts_rank is based only on frequencies of lexems
> and doesn't count distance between query lexems. Also, it supports only
> primitive queries.

Thanks.  Attached doc patch applied to head and 9.1.X.

---------------------------------------------------------------------------


>
> Oleg
> On Wed, 12 Oct 2011, Bruce Momjian wrote:
>
> > Bruce Momjian wrote:
> >> Mark wrote:
> >>>> There's some potentially useful information here:
> >>>> http://www.postgresql.org/docs/9.0/interactive/textsearch-controls.html#TEXTSEARCH-RANKING
> >>>
> >>> Thanks for reply. I was reading the documentation of PostgreSQL, but there
> >>> it is not written the name of the used methods. Everywhere there is written,
> >>> that ts_rank use standard ranking function. But it is difficult to say which
> >>> is the standard function.
> >>> Somewhere I found that it is maybe based on Vector space model and it seems
> >>> to be truth, because in the code of tsrank.c is counted the frequency of
> >>> words, but I am not sure of that :-(
> >>
> >> Oleg, Teodor, can you give me a description of how ts_rank decided how
> >> to rank items?  Thanks.
> >
> > Any news on this question?
> >
> >
>
>      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

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +
diff --git a/doc/src/sgml/textsearch.sgml b/doc/src/sgml/textsearch.sgml
new file mode 100644
index ef228e3..46db103
*** a/doc/src/sgml/textsearch.sgml
--- b/doc/src/sgml/textsearch.sgml
*************** ts_rank(<optional> <replaceable class="P
*** 867,873 ****

        <listitem>
         <para>
!         Standard ranking function.<!-- TODO document this better -->
         </para>
        </listitem>
       </varlistentry>
--- 867,873 ----

        <listitem>
         <para>
!         Ranks vectors based on the frequency of their matching lexems.
         </para>
        </listitem>
       </varlistentry>