RQL String Functions

RQL now includes a basic library of string functions. You can use these to slice and group your data
in arbitrary ways. For example, "email domains with the most events in the past hour":

SELECT substring(person.email, locate('@', person.email)), count(*)
FROM item_occurrence
WHERE timestamp >= unix_timestamp() - 3600 AND person.email IS NOT NULL
GROUP BY 1
ORDER BY 2 DESC

The new functions: concat, concat_ws, lower, upper, left, right, substring, locate, length,
char_length. The functions are implemented to be compatible with MySQL; see the
RQL docs for details.