tsearch2, gin and @@@ operator?

On Thu, 30 Aug 2007, Jean-Paul Argudo wrote:

Hi all,

I cant find in the docs about tsearch2 (nor the Oleg&Teodor's wiki) when
to use @@@ instead of @@.

it's written here
http://www.sai.msu.su/~megera/postgres/fts/doc/indexes-fts.html

@@ works in GIST, even with 'lexeme:a' (:a, :bc, etc.. every combination
of a,b,c & d part)

@@ doesnt with GIN in the same queries it, PostgreSQL says:

ERREUR: With class of lexeme restrictions use @@@ operation

I added a RAISE NOTICE as I can give you the query, generated from a
plpgsql function:

INFO: There was an error running this query:

select d.id, q
from documents_gin d,
to_tsquery('default_french', convert('chef:d', 'LATIN9')) q
where
gin_vector @@ q;

So, I have to use @@@ there instead of @@ to have the query working.

Now, I don't know when to use @@ or @@@.

Can I use always @@@ instead of @@ when its about a GIN based search?

If can use always @@@, is it less performant than @@ in some cases?

Please let me know when to use @@ or @@@ if I may not use allways @@@ in
those case, as I can tweak my plpgsql function.

Thanks a lot,

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