Re: Tsearch & functional indexes

Ron,

tsearch index is lossy, so search results needs to be verified.
If you have separate tsvector column you could use it and get all benefit
of to_tsvector already process documents (parsing, dictionaries lookup,...),
instead of reading entire document from disk and process it again.
Read tsearch2 internals for more info.
http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_internals

     Oleg
On Sun, 9 Oct 2005, Ron Mayer wrote:

>
> In the tsearch2 documentation I see a lot of examples where you
> add a column of type tsvector to your table and then indexing
> that column.
>
> Instead of adding the extra column, would it be possible to
> just make a functional index something like this:
>
>  create index foo__tsearch on foo using gist (to_tsvector('simple'::text,
> text))
>
> A brief informal experiment I tried suggests that
> the create index command works; but that queries
> using this approach were slower than having the
> column around.  I would have expected it to be faster,
> since the disk space used should have been smaller.
> Perhaps something about table statistics that I'm
> not considering?
>
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     Regards,
         Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83