No, that's not possible. Keep in mind that these expressions may be evaluated on the client or the server (it depends on the query). The could be evaluated on post aggregated rows too where the idea of which region no longer makes sense.

On Sat, Mar 25, 2017 at 10:15 PM Cheyenne Forbes <cheyenne.osanu.forbes@gmail.com> wrote:
or get the region of the table after calling:

        Expression arg = getChildren().get(0);
        if (!arg.evaluate(tuple, ptr)) {
            return false;
        }