@Override public Result implement(RelNode node) {
    return dispatch(node);
  }
Removes cast from string.

<p>For example, {@code x > CAST('2015-01-07' AS DATE)}
becomes {@code x > '2015-01-07'}.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/jdbc/HiveJdbcImplementor.java