@Override public Void visitCall(RexCall call) {
      if (!dialect.supportsDataType(call.getType())) {
        throw Util.FoundOne.NULL;
      }
      return super.visitCall(call);
    }
Returns whether a given expression contains only valid data types for this dialect.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/jdbc/JDBCProjectPushDownRule.java