Subquery union all with all constants order error

[sunsun314]

• dble version： master
• preconditions ：
  Order is error when subQuery with union and one of the union sql all are constants
• configs：

schema.xml

<?xml version="1.0"?>
<!DOCTYPE dble:schema SYSTEM "schema.dtd">
<dble:schema xmlns:dble="http://dble.cloud/">

    <schema name="TESTDB" dataNode = 'dn1'>
        <!-- auto sharding by id (long) -->
        <table name="BAMS_FLOW_LOG" dataNode="dn1,dn2" rule="sharding-by-hash2"/>
        <table name="travelrecord" dataNode="dn1,dn2" rule="sharding-by-hash2"/>
        <table name="date_table" dataNode="dn1,dn2,dn3" rule="sharding-by-date"/>  
        <!-- global table is auto cloned to all defined data nodes ,so can join
            with any table whose sharding node is in the same data node -->
        <table name="company" primaryKey="ID" type="global" dataNode="dn1,dn2,dn3,dn4"/>
        <table name="goods" primaryKey="ID" type="global" dataNode="dn1,dn2"/>
        <!-- random sharding using mod sharind rule -->
        <table name="hotnews" primaryKey="ID" autoIncrement="true" dataNode="dn1,dn2,dn3,dn4"
               rule="sharding-by-mod"/>
        <table name="customer" primaryKey="ID" dataNode="dn1,dn2"
               rule="sharding-by-mod">
            <childTable name="orders" primaryKey="ID" joinKey="customer_id"
                        parentKey="id">
                <childTable name="order_items" joinKey="order_id"
                            parentKey="id"/>
            </childTable>
            <childTable name="customer_addr" primaryKey="ID" joinKey="customer_id"
                        parentKey="id"/>
        </table>
    </schema>
    
     <schema name="xxxx" dataNode = 'dn1'> </schema>
    
    <!-- <dataNode name="dn1$0-743" dataHost="localhost1" database="db$0-743"
        /> -->
    <dataNode name="dn1" dataHost="localhost1" database="db1"/>
    <dataNode name="dn2" dataHost="localhost1" database="db2"/>
    <dataNode name="dn3" dataHost="localhost1" database="db3"/>
    <dataNode name="dn4" dataHost="localhost1" database="db4"/>
    <dataHost name="localhost1" maxCon="1000" minCon="10" balance="0" switchType="1" slaveThreshold="100">
        <heartbeat>show slave status</heartbeat>
        <!-- can have multi write hosts -->
        <writeHost host="hostM1" url="10.186.24.37:3306" user="root"
                   password="123456">
        </writeHost>
        
    </dataHost>
</dble:schema>

rule.xml

default

server.xml

default

• steps：
  execute sql
  SELECT
  BUSIDATE AS occurDate,
  ZONENO AS zoneNo,
  BRNO AS brNo,
  TELLERNO AS tellerNo
  FROM
  (
  SELECT
  F.BUSIDATE,
  F.ZONENO,
  F.BRNO,
  F.TELLERNO
  FROM
  BAMS_FLOW_LOG F
  where F.id = 1
  UNION ALL
  SELECT
  '20180716' AS BUSIDATE,
  '00119' AS ZONENO,
  '260' AS BRNO,
  '34890' AS TELLERNO
  ) T
• expect result：
  +-----------+--------+----------+----------+
  | occurDate | zoneNo | brNo | tellerNo |
  +-----------+--------+----------+----------+
  | 20180716 | 00119 | 260 | 34890 |
  +-----------+--------+----------+----------+
• real result：
  +-----------+--------+----------+----------+
  | occurDate | zoneNo | brNo | tellerNo |
  +-----------+--------+----------+----------+
  | 00119 | 260 | 20180716 | 34890 |
  +-----------+--------+----------+----------+

/label ~BUG

[FlyingMao]

verifird version5.6.29-dble-9.9.9.9-dc2f715-20180824075539