problems: slow queries with tsearch2

From: "Rafa Comino" <rafacomino(at)gmail(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: problems: slow queries with tsearch2
Date: 2007-02-16 17:39:33
Message-ID: bd8b58a40702160939j360c458et7ad727dcdfe1639a@mail.gmail.com
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Hi from Spain,

I have a problem with TSearch2,

I have a table with more than a million registers (a table of books, for
example),

I made a tsearch2 index for one of my fields (the title of the books, for
example),

I make queries from that table, over the tsearch2 index. Then some of my
queries get too much slowly, and I don't know how to resolve it. For
example:

- Every thing is ok, but when the query get a lot of results (about
1000 register) and I use ORDER BY over other field in the query (even if I
use LIMIT 10) the query gets slowly, 7 or 8 seconds. The thing is, that
query gets all the results and later order those results, and that makes my
query so slow. How can I resolve this.
- When my queries have two conditions joined with AND, and each
condition is made over a different tsearch2 index, the execution get first x
rows from the first condition, and y rows from the second condition, later
get the rows from both result set. This makes my queries slow too. How could
I resolve this?.

(Sorry for my English, and thanks for reading me)

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