hint sql error with multiple nodes

[yexiaoli88]

**dble version：version: 5.6.29-dble-9.9.9.9-84bb96d-20180824025838 **

schema.xml

<table name="test" dataNode="dn1,dn2,dn3,dn4" rule="sharding-by-mod" />

rule.xml

 <tableRule name="sharding-by-mod">
        <rule>
            <columns>id</columns>
            <algorithm>hashmod</algorithm>
        </rule>
    </tableRule>
<function name="hashmod" class="Hash">
        <property name="partitionCount">4</property>
        <property name="partitionLength">1</property>
    </function>

• steps：

1. MySQL [testdb]> /*!dble:datanode=dn1,dn2*/ select * from test;
+------+------+
| id   | name |
+------+------+
|   20 | dn1  |
|   50 | dn1  |
|    2 | dn1  |
+------+------+
3 rows in set (0.00 sec)

2. MySQL [testdb]> /*!dble:datanode=dn2,dn1*/ select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    1 | test1 |
|    5 | test5 |
+------+-------+
2 rows in set (0.00 sec)

3. MySQL [testdb]> /*!dble:datanode=dn1*/ select * from test;
+------+------+
| id   | name |
+------+------+
|   20 | dn1  |
|   50 | dn1  |
|    2 | dn1  |
+------+------+
3 rows in set (0.01 sec)

4. MySQL [testdb]> /*!dble:datanode=dn2*/ select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    1 | test1 |
|    5 | test5 |
+------+-------+
2 rows in set (0.00 sec)

5.MySQL [testdb]> select * from test;
+------+--------+
| id   | name   |
+------+--------+
|    1 | test1  |
|    5 | test5  |
|    3 | test3  |
|   20 | dn1    |
|   50 | dn1    |
|    2 | dn1    |
|    2 | test2  |
|   34 | test34 |
|   30 | test30 |
+------+--------+

• expect result：
  1. hint sql with multiple nodes return correct results
• real result：
  1. hint sql with multiple nodes return incorrect results

[yexiaoli88]

related #669 #649

[yexiaoli88]

incorrect when type= sql and sql more than 1

<table name="test_shard" dataNode="dn1,dn2,dn3,dn4" rule="sharding-by-mod" />

parepre tables:

    drop table if exists test;
    drop table if exists test_shard
    insert into test values(1,'test1'),(2,'test2'),(3,'test3'),(4,'test4'),(5,'test5');
    insert into test_shard values(1,'test_shard1'),(2,'test_shard2'),(3,'test_shard3'),(4,'test_shard4'),(5,'test_shard5');

steps:

1 MySQL [testdb]> /*!dble:sql=select id from test_shard where id=1,sql=select id from test_shard where id=2*/select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    2 | test2 |
|    9 | test9 |
+------+-------+
2 rows in set (0.01 sec)

2 MySQL [testdb]> /*!dble:sql=select id from test_shard where id=2,sql=select id from test_shard where id=1*/select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    1 | test1 |
|    5 | test5 |
+------+-------+
2 rows in set (0.00 sec)

3 MySQL [testdb]> /*!dble:sql=select id from test_shard where id=1*/select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    1 | test1 |
|    5 | test5 |
+------+-------+
2 rows in set (0.00 sec)

4 MySQL [testdb]> /*!dble:sql=select id from test_shard where id=2*/select * from test;
+------+-------+
| id   | name  |
+------+-------+
|    2 | test2 |
|    9 | test9 |
+------+-------+
2 rows in set (0.00 sec)

expect result: 1.step 1 and step 2 should get the same result which contains both step3 and step 4's results

[sunsun314]

All hint change to only support one input ,otherwise the router can not find right route result