create table sort_test(
id int,
name string
)
row format delimited
fields terminated by ' '
lines terminated by '
'
stored as textfile;
[root@wadeyu ~]# cat sort_test.log
4679 aaa
4728 aaa
3040 aaa
4207 aaa
2231 aaa
1279 aaa
7954 aaa
582 aaa
7096 aaa
4878 aaa
9684 aaa
1540 aaa
4826 aaa
2543 aaa
2323 aaa
1420 aaa
5083 aaa
8965 aaa
1391 aaa
9719 aaa
9901 aaa
2393 aaa
6024 aaa
444 aaa
1574 aaa
8881 aaa
5739 aaa
8689 aaa
1614 aaa
9340 aaa
6726 aaa
109 aaa
6941 aaa
9562 aaa
9019 aaa
4945 aaa
2206 aaa
5910 aaa
8552 aaa
1795 aaa
2720 aaa
9007 aaa
8377 aaa
2179 aaa
3683 aaa
5869 aaa
5448 aaa
5223 aaa
5127 aaa
4616 aaa
2340 aaa
1268 aaa
4332 aaa
2989 aaa
19 aaa
7880 aaa
505 aaa
5975 aaa
5288 aaa
5682 aaa
376 aaa
7502 aaa
6448 aaa
3774 aaa
5541 aaa
9636 aaa
2037 aaa
246 aaa
6151 aaa
7837 aaa
1506 aaa
3749 aaa
9335 aaa
3973 aaa
5160 aaa
7929 aaa
834 aaa
3451 aaa
1766 aaa
6228 aaa
8961 aaa
8177 aaa
2340 aaa
4245 aaa
3226 aaa
2670 aaa
784 aaa
7699 aaa
2054 aaa
6006 aaa
4204 aaa
8905 aaa
6182 aaa
1271 aaa
5415 aaa
5164 aaa
4320 aaa
3736 aaa
2287 aaa
6559 aaa
- Order By
- Job中只会启动一个reduce做全局排序，数据量大时，耗时会很久
- 在strict模式(hive.mapred.mode=strict)下，必须添加limit语句限制返回条数
# 语法格式
colOrder: ( ASC | DESC )
colNullOrder: (NULLS FIRST | NULLS LAST) -- (Note: Available in Hive 2.1.0 and later)
orderBy: ORDER BY colName colOrder? colNullOrder? (',' colName colOrder? colNullOrder?)*
query: SELECT expression (',' expression)* FROM src orderBy
# 排序
select * from sort_test order by id desc;
+---------------+-----------------+--+
| sort_test.id | sort_test.name |
+---------------+-----------------+--+
| 9901 | aaa |
| 9719 | aaa |
| 9684 | aaa |
| 9636 | aaa |
| 9562 | aaa |
| 9340 | aaa |
| 9335 | aaa |
| 9019 | aaa |
| 9007 | aaa |
| 8965 | aaa |
| 8961 | aaa |
| 8905 | aaa |
| 8881 | aaa |
| 8689 | aaa |
| 8552 | aaa |
| 8377 | aaa |
| 8177 | aaa |
| 7954 | aaa |
| 7929 | aaa |
| 7880 | aaa |
| 7837 | aaa |
| 7699 | aaa |
| 7502 | aaa |
| 7096 | aaa |
| 6941 | aaa |
| 6726 | aaa |
| 6559 | aaa |
| 6448 | aaa |
| 6228 | aaa |
| 6182 | aaa |
| 6151 | aaa |
| 6024 | aaa |
| 6006 | aaa |
| 5975 | aaa |
| 5910 | aaa |
| 5869 | aaa |
| 5739 | aaa |
| 5682 | aaa |
| 5541 | aaa |
| 5448 | aaa |
| 5415 | aaa |
| 5288 | aaa |
| 5223 | aaa |
| 5164 | aaa |
| 5160 | aaa |
| 5127 | aaa |
| 5083 | aaa |
| 4945 | aaa |
| 4878 | aaa |
| 4826 | aaa |
| 4728 | aaa |
| 4679 | aaa |
| 4616 | aaa |
| 4332 | aaa |
| 4320 | aaa |
| 4245 | aaa |
| 4207 | aaa |
| 4204 | aaa |
| 3973 | aaa |
| 3774 | aaa |
| 3749 | aaa |
| 3736 | aaa |
| 3683 | aaa |
| 3451 | aaa |
| 3226 | aaa |
| 3040 | aaa |
| 2989 | aaa |
| 2720 | aaa |
| 2670 | aaa |
| 2543 | aaa |
| 2393 | aaa |
| 2340 | aaa |
| 2340 | aaa |
| 2323 | aaa |
| 2287 | aaa |
| 2231 | aaa |
| 2206 | aaa |
| 2179 | aaa |
| 2054 | aaa |
| 2037 | aaa |
| 1795 | aaa |
| 1766 | aaa |
| 1614 | aaa |
| 1574 | aaa |
| 1540 | aaa |
| 1506 | aaa |
| 1420 | aaa |
| 1391 | aaa |
| 1279 | aaa |
| 1271 | aaa |
| 1268 | aaa |
| 834 | aaa |
| 784 | aaa |
| 582 | aaa |
| 505 | aaa |
| 444 | aaa |
| 376 | aaa |
| 246 | aaa |
| 109 | aaa |
| 19 | aaa |
+---------------+-----------------+--+
- Sort By
- 排序前会根据排序字段分区，一个job启动多个reduce进行局部排序
- 如果有limit语句，会再次启动一个job，取出每个局部排好序的前n条，再进行全局排序
- 只保证局部有序，不保证全局有序
# Sort By语法
colOrder: ( ASC | DESC )
sortBy: SORT BY colName colOrder? (',' colName colOrder?)*
query: SELECT expression (',' expression)* FROM src sortBy
# 设置开启的reduce个数
set mapreduce.job.reduces=2;
0: jdbc:hive2://> set mapreduce.job.reduces;
+--------------------------+--+
| set |
+--------------------------+--+
| mapreduce.job.reduces=2 |
+--------------------------+--+
# 执行局部排序（未带limit）
0: jdbc:hive2://> select * from sort_test sort by id desc;
+---------------+-----------------+--+
| sort_test.id | sort_test.name |
+---------------+-----------------+--+
| 9901 | aaa |
| 9684 | aaa |
| 9340 | aaa |
| 9019 | aaa |
| 9007 | aaa |
| 8965 | aaa |
| 8961 | aaa |
| 8689 | aaa |
| 8552 | aaa |
| 8177 | aaa |
| 7837 | aaa |
| 7699 | aaa |
| 7502 | aaa |
| 6559 | aaa |
| 6448 | aaa |
| 6228 | aaa |
| 6024 | aaa |
| 6006 | aaa |
| 5975 | aaa |
| 5910 | aaa |
| 5869 | aaa |
| 5739 | aaa |
| 5682 | aaa |
| 5541 | aaa |
| 5448 | aaa |
| 5415 | aaa |
| 5288 | aaa |
| 5164 | aaa |
| 5160 | aaa |
| 5083 | aaa |
| 4878 | aaa |
| 4826 | aaa |
| 4679 | aaa |
| 4616 | aaa |
| 4245 | aaa |
| 4207 | aaa |
| 3736 | aaa |
| 3451 | aaa |
| 3226 | aaa |
| 3040 | aaa |
| 2989 | aaa |
| 2720 | aaa |
| 2670 | aaa |
| 2340 | aaa |
| 2231 | aaa |
| 2206 | aaa |
| 2054 | aaa |
| 2037 | aaa |
| 1766 | aaa |
| 1614 | aaa |
| 1540 | aaa |
| 1506 | aaa |
| 1420 | aaa |
| 1268 | aaa |
| 834 | aaa |
| 784 | aaa |
| 582 | aaa |
| 444 | aaa |
| 376 | aaa |
| 246 | aaa |
| 19 | aaa |
| 9719 | aaa |
| 9636 | aaa |
| 9562 | aaa |
| 9335 | aaa |
| 8905 | aaa |
| 8881 | aaa |
| 8377 | aaa |
| 7954 | aaa |
| 7929 | aaa |
| 7880 | aaa |
| 7096 | aaa |
| 6941 | aaa |
| 6726 | aaa |
| 6182 | aaa |
| 6151 | aaa |
| 5223 | aaa |
| 5127 | aaa |
| 4945 | aaa |
| 4728 | aaa |
| 4332 | aaa |
| 4320 | aaa |
| 4204 | aaa |
| 3973 | aaa |
| 3774 | aaa |
| 3749 | aaa |
| 3683 | aaa |
| 2543 | aaa |
| 2393 | aaa |
| 2340 | aaa |
| 2323 | aaa |
| 2287 | aaa |
| 2179 | aaa |
| 1795 | aaa |
| 1574 | aaa |
| 1391 | aaa |
| 1279 | aaa |
| 1271 | aaa |
| 505 | aaa |
| 109 | aaa |
+---------------+-----------------+--+
# 带limit排序(会额外再启动一个job进行全局排序)
0: jdbc:hive2://> select * from sort_test sort by id desc limit 300;
+---------------+-----------------+--+
| sort_test.id | sort_test.name |
+---------------+-----------------+--+
| 9901 | aaa |
| 9719 | aaa |
| 9684 | aaa |
| 9636 | aaa |
| 9562 | aaa |
| 9340 | aaa |
| 9335 | aaa |
| 9019 | aaa |
| 9007 | aaa |
| 8965 | aaa |
| 8961 | aaa |
| 8905 | aaa |
| 8881 | aaa |
| 8689 | aaa |
| 8552 | aaa |
| 8377 | aaa |
| 8177 | aaa |
| 7954 | aaa |
| 7929 | aaa |
| 7880 | aaa |
| 7837 | aaa |
| 7699 | aaa |
| 7502 | aaa |
| 7096 | aaa |
| 6941 | aaa |
| 6726 | aaa |
| 6559 | aaa |
| 6448 | aaa |
| 6228 | aaa |
| 6182 | aaa |
| 6151 | aaa |
| 6024 | aaa |
| 6006 | aaa |
| 5975 | aaa |
| 5910 | aaa |
| 5869 | aaa |
| 5739 | aaa |
| 5682 | aaa |
| 5541 | aaa |
| 5448 | aaa |
| 5415 | aaa |
| 5288 | aaa |
| 5223 | aaa |
| 5164 | aaa |
| 5160 | aaa |
| 5127 | aaa |
| 5083 | aaa |
| 4945 | aaa |
| 4878 | aaa |
| 4826 | aaa |
| 4728 | aaa |
| 4679 | aaa |
| 4616 | aaa |
| 4332 | aaa |
| 4320 | aaa |
| 4245 | aaa |
| 4207 | aaa |
| 4204 | aaa |
| 3973 | aaa |
| 3774 | aaa |
| 3749 | aaa |
| 3736 | aaa |
| 3683 | aaa |
| 3451 | aaa |
| 3226 | aaa |
| 3040 | aaa |
| 2989 | aaa |
| 2720 | aaa |
| 2670 | aaa |
| 2543 | aaa |
| 2393 | aaa |
| 2340 | aaa |
| 2340 | aaa |
| 2323 | aaa |
| 2287 | aaa |
| 2231 | aaa |
| 2206 | aaa |
| 2179 | aaa |
| 2054 | aaa |
| 2037 | aaa |
| 1795 | aaa |
| 1766 | aaa |
| 1614 | aaa |
| 1574 | aaa |
| 1540 | aaa |
| 1506 | aaa |
| 1420 | aaa |
| 1391 | aaa |
| 1279 | aaa |
| 1271 | aaa |
| 1268 | aaa |
| 834 | aaa |
| 784 | aaa |
| 582 | aaa |
| 505 | aaa |
| 444 | aaa |
| 376 | aaa |
| 246 | aaa |
| 109 | aaa |
| 19 | aaa |
+---------------+-----------------+--+
- Order By 和 Sort By区别
- Order By全局排序，Sort By局部排序
- 取TopN时，Sort By 比 Order By效率更高
- Distribute By
- 查询语句对指定字段分组
- 通常结合Sort By语句使用，比如同一个地区，不同商家排序，就需要用到这个
- Cluster By
- 分组且排序，等价于 Distribute By 和 Sort By 的结合
-- 使用示例
SELECT col1, col2 FROM t1 CLUSTER BY col1
SELECT col1, col2 FROM t1 DISTRIBUTE BY col1
SELECT col1, col2 FROM t1 DISTRIBUTE BY col1 SORT BY col1 ASC, col2 DESC
参考资料
【0】Hive wiki - LanguageManual SortBy