hive+python 入门

徐冬丽

自己写的一个简单例子，用来做话题描述去重，表中的desc字段 “a-b-a-b-b-c”需要去重
python代码如下：
#!/usr/bin/python
import sys
reload(sys)
sys.setdefaultencoding('utf8')
def quchong(desc):
a=desc.split('-')
return '-'.join(set(a))
while True:
line = sys.stdin.readline()
if line == "":
break
line = line.rstrip('\n')
# your process code here
parts = line.split('\t')
parts[2]=quchong(parts[2])
print "\t".join(parts)
下面是转载过来的，比较详细
二、hive map中字段自增的写法（转）
分类： hadoop 2010-09-03 16:01 99人阅读 评论(0) 收藏 举报
1、建立表结构
hive> CREATE TABLE t3 (foo STRING, bar MAP<STRING,INT>)
> ROW FORMAT DELIMITED
> FIELDS TERMINATED BY '/t'
> COLLECTION ITEMS TERMINATED BY ','
> MAP KEYS TERMINATED BY ':'
> STORED AS TEXTFILE;
OK

2、建成的效果
hive> describe t3;
OK
foo     string
bar     map<string,int>

3、生成test.txt
jeffgeng        click:13,uid:15

4、把test.txt load进来
hive> LOAD DATA LOCAL INPATH 'test.txt' OVERWRITE INTO TABLE t3;
Copying data from file:/root/src/hadoop/hadoop-0.20.2/contrib/hive-0.5.0-bin/bin/test.txt
Loading data to table t3
OK

load完效果如下
hive> select * from t3;
OK
jeffgeng        {"click":13,"uid":15}

5、可以这样查map的值
hive> select bar['click'] from t3;
...一系列的mapreduce...
OK
13

6、编写add_mapper
#!/usr/bin/python
import sys
import datetime
for line in sys.stdin:
line = line.strip()
foo, bar = line.split('/t')
d = eval(bar)
d['click'] += 1
print '/t'.join([foo, str(d)])

7、在hive中执行
hive> CREATE TABLE t4 (foo STRING, bar MAP<STRING,INT>)
> ROW FORMAT DELIMITED
> FIELDS TERMINATED BY '/t'
> COLLECTION ITEMS TERMINATED BY ','
> MAP KEYS TERMINATED BY ':'
> STORED AS TEXTFILE;

hive> add FILE add_mapper.py

INSERT OVERWRITE TABLE t4
> SELECT
>   TRANSFORM (foo, bar)
>   USING 'python add_mapper.py'
>   AS (foo, bar)
> FROM t3;
FAILED: Error in semantic analysis: line 1:23 Cannot insert into target table because column number/types are different t4: Cannot convert column 1 from string to map<string,int>.

8、为什么会报出以上错误？貌似add_mapper.py的输出是string格式的，hive无法此这种格式的map认出。后查明，AS后边可以为字段强制指定类型
INSERT OVERWRITE TABLE t4
SELECT
TRANSFORM (foo, bar)
USING 'python add_mapper.py'
AS (foo string, bar map<string,int>)
FROM t3;

9、同时python脚本要去除字典转换后遗留下来的空格，引号，左右花排号等
#!/usr/bin/python
import sys
import datetime
for line in sys.stdin:
line = line.strip('/t')
foo, bar = line.split('/t')
d = eval(bar)
d['click'] += 1
d['uid'] += 1
strmap = ''
for x in str(d):
if x in (' ', "'"):
continue
strmap += x
print '/t'.join([foo, strmap])

10、执行后的结果
hive> select * from t4;
OK
jeffgeng        {"click":14,"uid":null}
Time taken: 0.146 seconds
uid没有自增，原因待查