Some further thought about bug #7867 suggested that what's probably happening is the submitter's installation doesn't think that any of the Cyrillic letters are letters, so that no trigrams are identified in either string. Whereupon you get a 0/0 result from cnt_sml:
regression=# select similarity('', ''); similarity ------------ NaN (1 row) What should we have it return instead? In this case "1" might seem like the natural answer, but we could easily have very different strings that don't contain any trigrams: regression=# select similarity('---', '#######'); similarity ------------ NaN (1 row) Although I can see a case for returning 1, I'm inclined to think that returning 0 is a better idea. Thoughts? regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers