Help for performance

Hello!

I have two tables:

ns_article has about 2000 entries, and ns_word has about 2000000.

ns_word is a word-index for the article. I want to implement a
word-search in it.
I want to implement a search function, which can search with "like
'wordstart%'". I need to do it with a lot of keywords like altavista
does (with +: intersect, without +: union; with -: except), but I
haven't found any fast result.

The following query tree would be good:
- sort by atime
- index scan on ns_article (by article_id)
hash join:
- intersect/union/except
- index scan on ns_word (by index_word)
- index scan on ns_word (by index_word)
...

My current solution is:
(select distinct atime(get_ns_article(article_id)) as a, article_id
from ns_word where index_word like 'wordstart%') union (...)
intersect (...) order by a;

But this is VERY slow if I search with more than one keyword (when
intersect/union is on use). It is quite fast for one keyword (like
this: select distinct atime(get_ns_article(article_id)) as a,
article_id from ns_word where index_word like 'linux%').

the get_ns_artcile is a function which returns a tuple from the
ns_article table by an article_id.

Please help me to make it faster! We have enough memory, so this is
not a problem!

Thanks again,

dLux

--------------------------------------
Here are the table defs:
create table ns_article (
article_id int not null default nextval('ns_article_seq'),
site text,
atime timestamp,
...
);

create unique index ns_article_pkey on ns_article (article_id);
create unique index ns_article_url_title on ns_article (url,title);
create index ns_article_atime on ns_article (atime);

create table ns_word (
article_id int, -- cikk száma
orig_word text,
index_word text,
word_position int
);

create index ns_word_index_word on ns_word (index_word);
create unique index ns_word_article_wordpos on ns_word (article_id,
word_position);

dLux
--
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