I've got a table with a few million rows, consisting of a single text column. The average length is about 17 characters. For the sake of an experiment, I put a trigram index on that table. Unfortunately, % queries without smallish LIMITs are ridiculously slow (they take longer than an hour). A full table scan with a "WHERE similarity(...) >= 0.4" clause completes in just a couple of minutes. The queries only select a few hundred rows, so an index scan has got a real chance to be faster than a sequential scan. Am I missing something? Or are trigrams just a poor match for my data set? Are the individual strings too long, maybe? (This is with PostgreSQL 8.2.0, BTW.) -- Florian Weimer <fweimer@xxxxxx> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
