Hive中的数据分区

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首先认识什么是分区


Hive 中的分区就是分目录,把一个大的数据集根据业务需要分割成更下的数据集。



1. 如何定义分区,创建分区 


hivecreate table test(name string,sex int) partitioned by (birth string, age string);

Time taken: 0.044 seconds
hive> alter table test  add partition (birth='1980', age ='30');


Time taken: 0.079 seconds
hive> alter table test  add partition (birth='1981', age ='29');


Time taken: 0.052 seconds
hive> alter table test  add partition (birth='1982', age ='28');


Time taken: 0.056 seconds
hive> show partitions test;

birth=1980/age =30

birth=1981/age =29

birth=1982/age =28



2. 如何删除分区


hive> alter table test drop partition (birth='1980',age='30');


3. 加载数据到指定分区


load data local inpath '/home/hadoop/data.log' overwrite into table 

test partition(birth='1980-01-01',age='30');


创建分区原则: 最少粒度原则


4 向partition_test的分区中插入数据:

hive> insert overwrite table partition_test partition(stat_date='20110728',province='henan') select member_id,name from partition_test_input where stat_date='20110728' and province='henan';

还可以同时向多个分区插入数据,0.7版本以后不存在的分区会自动创建,0.6之前的版本官方文档上说必须要预先创建好分区:

hive>
> from partition_test_input
> insert overwrite table partition_test partition (stat_date='20110526',province='liaoning')
> select member_id,name where stat_date='20110526' and province='liaoning'
> insert overwrite table partition_test partition (stat_date='20110728',province='sichuan')
> select member_id,name where stat_date='20110728' and province='sichuan'
> insert overwrite table partition_test partition (stat_date='20110728',province='heilongjiang')
> select member_id,name where stat_date='20110728' and province='heilongjiang';
Total MapReduce jobs = 4

http://biansutao.blog.163.com/blog/static/6702418820115332453560/

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