WHERE clause in SELECT DISTINCT can be ignored

I've tested this out on 2.1-head. I'm not sure if it's the same behavior on newer versions.

For a given table t, with PRIMARY KEY (id, v) the following two queries return the same result:
SELECT DISTINCT id FROM t WHERE v > X ALLOW FILTERING
SELECT DISTINCT id FROM t

The WHERE clause in the former is silently ignored, and all id are returned, regardless of the value of v in any row.

It seems like this has been a known issue for a while:
http://stackoverflow.com/questions/26548788/select-distinct-cql-ignores-where-clause

However, if we don't support filtering on anything but the partition key, we should reject the query, rather than silently dropping the where clause