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Re: Tsearch & functional indexes

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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@xxxxxxxxxx, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83

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