分页查询，路由多个分片，只有一个分片有数据，返回结果集不正确

[along101]

Please answer these questions before submitting your issue. Thanks!

Which version of Sharding-Jdbc do you using?

1.4.2

Expected behavior

分页查询，select * from t_order limit 2,2 路由多个分片，只有一个分片有数据，查询4条记录

Actual behavior

应该只返回2条记录

Steps to reproduce the behavior

sharding-jdbc-example-mybatis这个demo工程中，增加测试类
`
package com.dangdang.ddframe.rdb.sharding.example.jdbc;
import com.dangdang.ddframe.rdb.sharding.example.jdbc.entity.Order;
import com.dangdang.ddframe.rdb.sharding.example.jdbc.repository.OrderRepository;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.util.List;

public class Test {
public static void main(final String[] args) {
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("META-INF/mybatisContext.xml");
OrderRepository orderRepository = applicationContext.getBean(OrderRepository.class);
List ls = orderRepository.selectAll();
System.out.println(ls);
}
}

`

修改OrderMapper.xml最后一个查询，增加limit
`

<select id="selectAll" resultMap="baseResultMap">
    SELECT
    <include refid="baseColumnList"/>
    FROM `t_order` limit 2,2
</select>

修改数据库数据：
delete from ds_0.t_order_0;
delete from ds_0.t_order_1;
delete from ds_1.t_order_0;
delete from ds_1.t_order_1;

INSERT INTO ds_0.t_order_0 VALUES (1000, 10, 'INIT');
INSERT INTO ds_0.t_order_0 VALUES (1002, 10, 'INIT');
INSERT INTO ds_0.t_order_0 VALUES (1004, 10, 'INIT');
INSERT INTO ds_0.t_order_0 VALUES (1006, 10, 'INIT');
INSERT INTO ds_0.t_order_0 VALUES (1008, 10, 'INIT');
`

执行打印结果有4条记录：
[order_id: 1000, user_id: 10, status: INIT, order_id: 1002, user_id: 10, status: INIT, order_id: 1004, user_id: 10, status: INIT, order_id: 1006, user_id: 10, status: INIT]

调试代码发现，shardingJDBC在包装结果集时，根据mergeContext判断是不是要聚合，ResultSetFactory.getResultSet方法中
ShardingResultSets shardingResultSets = new ShardingResultSets(resultSets);
传入的resultSets有4个rs，获取到的shardingResultSets 只有一个，因为只有一个rs有数据，
ShardingResultSets.filterResultSets方法会过滤掉没有记录的rs
`

private List filterResultSets(final List resultSets) throws SQLException {
List result = new ArrayList<>(resultSets.size());
for (ResultSet each : resultSets) {
if (each.next()) {
result.add(new WrapperResultSet(each));
}
}
return result;
}
`

这样的话在shardingResultSets.getType()返回的是SINGLE
`

switch (shardingResultSets.getType()) {
case EMPTY:
return buildEmpty(resultSets);
case SINGLE:
return buildSingle(shardingResultSets);
case MULTIPLE:
return buildMultiple(shardingResultSets, mergeContext);
default:
throw new UnsupportedOperationException(shardingResultSets.getType().toString());
}
`
这样就不会去做合并结果集操作了

Please provide the reproduce example codes (such as github link) if possible.

[terrymanu]

这个问题已经在1.5.0.M2修复了
duplicate with #239