no comments before Rick post tsearch configs and increased buffers !
Union shouldn't be faster than (term1|term2).
tsearch2 internals description might help you understanding tsearch2 
See  http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_internals
Also, don't miss my notes:

On Tue, 22 Mar 2005, Mike Rylander wrote:

On Tue, 22 Mar 2005 14:25:19 +0100, Rick Jansen <[EMAIL PROTECTED]> wrote:

ilab=# explain analyze select count(titel) from books where idxfti @@ to_tsquery('default', 'buckingham | palace'); QUERY PLAN ---------------------------------------------------------------------------------------------------------------------------------------- Aggregate (cost=35547.99..35547.99 rows=1 width=56) (actual time=125968.119..125968.120 rows=1 loops=1) -> Index Scan using idxfti_idx on books (cost=0.00..35525.81 rows=8869 width=56) (actual time=0.394..125958.245 rows=3080 loops=1) Index Cond: (idxfti @@ '\'buckingham\' | \'palac\''::tsquery) Total runtime: 125968.212 ms (4 rows)

Time: 125969.264 ms

Ahh... I should have qualified my claim. I am creating a google-esqe search interface and almost every query uses '&' as the term joiner. 'AND' queries and one-term queries are orders of magnitude faster than 'OR' queries, and fortunately are the expected default for most users. (Think, "I typed in these words, therefore I want to match these words"...) An interesting test may be to time multiple queries independently, one for each search term, and see if the combined cost is less than a single 'OR' search. If so, you could use UNION to join the results.

However, the example you originally gave ('terminology') should be
very fast.  On a comparable query ("select count(value) from
metabib.full_rec where index_vector @@ to_tsquery('default','jane');")
I get 12ms.

Oleg, do you see anything else on the surface here?


 SELECT titel FROM books WHERE idxfti @@
   to_tsquery('default', 'buckingham')
 SELECT titel FROM books WHERE idxfti @@
   to_tsquery('default', 'palace');

and see if using '&' instead of '|' where you can helps out.  I
imagine you'd be surprised by the speed of:

 SELECT titel FROM books WHERE idxfti @@
   to_tsquery('default', 'buckingham&palace');

> As an example of what I think you *should* be seeing, I have a similar > box (4 procs, but that doesn't matter for one query) and I can search > a column with tens of millions of rows in around a second. >

That sounds very promising, I'd love to get those results.. could you
tell me what your settings are, howmuch memory you have and such?

16G of RAM on a dedicated machine.

shared_buffers = 15000 # min 16, at least max_connections*2, 8KB each work_mem = 10240 # min 64, size in KB maintenance_work_mem = 1000000 # min 1024, size in KB # big m_w_m for loading data...

random_page_cost = 2.5          # units are one sequential page fetch cost
# fast drives, and tons of RAM

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

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