Hive分區表新增字段，查詢為Null

1.問題

在開發過程中，向hive分區表新增字段，發現查詢新增字段的值為NULL

2.問題復現

1.創建分區表，並插入數據

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，插入數據

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.驗證

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

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

但是 impala查詢正常

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

4.結論

1. 分區在增加字段前存在，會出現查詢新增字段值為NULL的情況
2. 分區在增加字段前不存在，正常

3.解決方法

對於在增加字段前已經存在的分區，必須再執行

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

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