On 9 Apr 2011, at 8:18pm, Igor Tandetnik wrote: > Simon Slavin <slav...@bigfraud.org> wrote: >> On 8 Apr 2011, at 2:34pm, Vadim Smirnov wrote: >> >>> Tbl1(id1 INTEGER, id2 INTEGER, str TEXT) 2 records >>> Tbl2(id INTEGER, Tbl1_id INTEGER, str TEXT) ~5000 records >>> And SQL-query: SELECT Tbl2.id, MY_FUNC(Tbl1.str, Tbl2.str) FROM Tbl2 JOIN >>> Tbl1 ON Tbl1.id1=Tbl2.Tbl1_id WHERE Tbl2.id>1000 AND >>> Tbl1.id2=1 LIMIT 50 We expected that MY_FUNC would be evaluated 50 times at >>> most, but it appeared 10000! >>> Why so? >> >> Your SELECT consists of a JOIN which tells SQLite to try every combination >> of one record from each table. For each combination >> it checks to see that all the conditions you gave are true. > > But the custom function is not involved in the WHERE clause. There doesn't > seem to be any reason to call it for rows that aren't going to be returned.
I guess either EXPLAIN or EXPLAIN QUERY PLAN would be helpful in figuring out what's going on. Simon. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
