Re: Why not keeping positions in GIN?

On Fri, 25 May 2007, Hitoshi Harada wrote:

> Hi,
>
> I was walking through GIN am source code these days, and found that it has
> only posting lists but no positions related those.
>
> The reason I was doing that is, to try to implement n-gram text search index
> on GIN for myself. As you know Japanese is not like English or other
> European languages. If you write Japanese (or other 'not separated') text
> index by n-gram, it should have entry positions on the entry as well as the
> posting lists, because you must know if each split query key are joined with
> each other in the data. To know this, position must be there.

FYI, Tatsuo uses tsearch2 for indexing japanese documents. But I agree,
n-gram index would be more universal for asian languages.

>
> It's not only about Japanese. When you search "phrase" for text in English,
> the same logic above will be needed. I don't research about tsearch2 but is
> there any problem?? Also, in some case int-array inverted index needs the
> entry positions as well, I guess. Obtaining positions with posting lists is
> "general" enough for GIN, isn't it?
>
> Is there any future plan around it?

Yes, we do have plans. See our todo, http://www.sai.msu.su/~megera/wiki/todo
You may read also FTSBOOK, http://www.sai.msu.su/~megera/postgres/fts/doc
and slides from PGCon2007, http://www.sai.msu.su/~megera/postgres/talks/fts-pgcon2007.pdf
>
>
> Regards,
>
> Hitoshi Harada
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org
>

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