Improve performance on DB queries

We have ~60,000 records in our redirect table and the queries are not using an index and are generally running at 200+ ms per query (one on every page).

The query is generally using a condition on the source and language tables so an index on this would improve performance no end.

I've attached a patch, the only problem with which is the length of time it takes to create the index on large tables.

mysql> SELECT redirect.rid AS rid FROM redirect redirect WHERE ( (source LIKE 'home' ESCAPE '\\') OR (source = '') )AND (language IN ('en', 'und'));
Empty set (0.20 sec)

mysql> create index source_language on redirect (source,language);
Query OK, 60283 rows affected (26.76 sec)
Records: 60283  Duplicates: 0  Warnings: 0

mysql> SELECT redirect.rid AS rid FROM redirect redirect WHERE ( (source LIKE 'home' ESCAPE '\\') OR (source = '') )AND (language IN ('en', 'und'));
Empty set (0.00 sec)