回退分组的代码修复bug
Merge branch 'master' of https://github.com/opencloudb/Mycat-Server

Conflicts:
	src/main/java/org/opencloudb/mpp/DataMergeService.java
	src/main/java/org/opencloudb/mpp/MutiDataMergeService.java
mpp 框架优化 ，一个线程异步执行
MPP异步优化，一个线程异步执行
Merge pull request #21 from opencloudb/master

mpp 框架优化 ，一个线程异步执行
druidparser limit逻辑错误（select * from tableName limit 2查出4条结果）
MPP 单线程异步Job Bug导致排序出现空指针的Bug修复
Merge pull request #23 from opencloudb/master

MPP 单线程异步Job Bug导致排序出现空指针的Bug修复
Merge pull request #22 from wdw1206/master

druidparser limit逻辑错误（select * from tableName limit 2查出4条结果）
删除排序的重复代码，默认改为堆排序
Merge pull request #24 from opencloudb/master

删除排序的重复代码，默认改为堆排序
Merge branch 'master' of https://github.com/opencloudb/Mycat-Server

Conflicts:
	src/main/java/org/opencloudb/mpp/DataMergeService.java
Merge branch 'master' of https://github.com/opencloudb/Mycat-Server

Conflicts:
	src/main/java/org/opencloudb/mpp/DataMergeService.java
resolve conflict

Conflicts:
	src/main/java/org/opencloudb/mpp/DataMergeService.java
Merge branch 'master' of https://github.com/opencloudb/Mycat-Server
解决测试程序问题
Update HeapItf.java

区分升降序
Merge pull request #27 from coderczp/patch-2

Update HeapItf.java
重构代码区分升降序

重构代码区分升降序
重构代码区分升降序

重构代码区分升降序