hive建表设置如果为null_Hive分区表新增字段，查询为Null

1.问题

在开发过程中，向hive分区表新增字段，发现查询新增字段的值为NULL

2.问题复现

1.创建分区表，并插入数据

create table student(id int,name string) partitioned by (dt string);

insert into table student partition(dt = '2019-11-13') select 1,'zhangsan';

insert into table student partition(dt = '2019-11-14') select 2,'lisi';

select * from student where dt = '2019-11-13';

select * from student where dt = '2019-11-14';

2.增加字段，插入数据

alter table student add columns(sex string)；

insert into table student partition(dt = '2019-11-13') select 1,'zhangsan','male';

insert into table student partition(dt = '2019-11-14') select 2,'lisi','female';

insert into table student partition(dt = '2019-11-15') select 3,'wangwu','female';

3.验证

select * from student where dt = '2019-11-13';

select * from student where dt = '2019-11-14';

但是 impala查询正常

select * from student where dt = '2019-11-15';

4.结论

分区在增加字段前存在，会出现查询新增字段值为NULL的情况

分区在增加字段前不存在，正常

3.解决方法

对于在增加字段前已经存在的分区，必须再执行

alter table student paritition(dt = '2019-11-14') add columns(sex string)；

select * from student where dt = '2019-11-14';