Error on `select +db_name.tbl_name.col_name`

[FlyingMao]

steps:

mysql> create table test_shard (id int(11) primary key,R_REGIONKEY float,R_NAME varchar(50),R_COMMENT varchar(50));                                 
Query OK, 0 rows affected (0.03 sec)

mysql> insert into test_shard (id,R_REGIONKEY,R_NAME,R_COMMENT) values (1,1, 'a string','test001'),(3,3, 'another string','test003');
Query OK, 2 rows affected (0.01 sec)

mysql> select mytest.test_shard.R_NAME from test_shard;
ERROR 1064 (HY000): com.alibaba.druid.sql.ast.expr.SQLPropertyExpr cannot be cast to com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr

log:

2017-09-19 15:56:29.090  WARN [BusinessExecutor1] (com.actiontech.dble.server.ServerConnection.executeException(ServerConnection.java:285)) - ServerConnection [id=5, schema=mytest, host=127.0.0.1, user=test,txIsolation=3, autocommit=true, schema=mytest]select mytest.test_shard.R_NAME from test_shard err:java.lang.ClassCastException: com.alibaba.druid.sql.ast.expr.SQLPropertyExpr cannot be cast to com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr
java.lang.ClassCastException: com.alibaba.druid.sql.ast.expr.SQLPropertyExpr cannot be cast to com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr
	at com.actiontech.dble.plan.visitor.MySQLItemVisitor.endVisit(MySQLItemVisitor.java:431) ~[dble-2.17.08.0.jar:?]
	at com.alibaba.druid.sql.ast.expr.SQLPropertyExpr.accept0(SQLPropertyExpr.java:71) ~[druid-1.0.31.jar:1.0.31]
	at com.alibaba.druid.sql.ast.SQLObjectImpl.accept(SQLObjectImpl.java:41) ~[druid-1.0.31.jar:1.0.31]
	at com.actiontech.dble.route.parser.druid.impl.DruidSelectParser.isSumFunc(DruidSelectParser.java:258) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.parser.druid.impl.DruidSelectParser.parseAggExprCommon(DruidSelectParser.java:216) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.parser.druid.impl.DruidSelectParser.parseAggGroupCommon(DruidSelectParser.java:306) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.parser.druid.impl.DruidSelectParser.parseOrderAggGroupMysql(DruidSelectParser.java:177) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.parser.druid.impl.DruidSelectParser.visitorParse(DruidSelectParser.java:113) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.parser.druid.impl.DefaultDruidParser.parser(DefaultDruidParser.java:47) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.util.RouterUtil.routeFromParser(RouterUtil.java:117) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.impl.DefaultRouteStrategy.routeNormalSqlWithAST(DefaultRouteStrategy.java:59) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.impl.AbstractRouteStrategy.route(AbstractRouteStrategy.java:45) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.route.RouteService.route(RouteService.java:105) ~[dble-2.17.08.0.jar:?]
	at com.actiontech.dble.server.ServerConnection.routeEndExecuteSQL(ServerConnection.java:232) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.server.ServerConnection.execute(ServerConnection.java:176) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.server.handler.SelectHandler.handle(SelectHandler.java:96) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.server.ServerQueryHandler.query(ServerQueryHandler.java:62) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.net.FrontendConnection.query(FrontendConnection.java:299) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.net.FrontendConnection.query(FrontendConnection.java:317) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.net.handler.FrontendCommandHandler.handleData(FrontendCommandHandler.java:65) [dble-2.17.08.0.jar:?]
	at com.actiontech.dble.net.handler.FrontendCommandHandler$1.run(FrontendCommandHandler.java:117) [dble-2.17.08.0.jar:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) [?:1.7.0_05]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) [?:1.7.0_05]
	at java.lang.Thread.run(Thread.java:722) [?:1.7.0_05]