hive修改表模式

留个备份。

hive用户可以通过alter语句更改table属性

Alter Partitions
增加partitions：

 ALTER TABLE table_name
       ADD [IF NOT EXISTS]
       PARTITION partition_spec [LOCATION 'location1']
                 partition_spec [LOCATION 'location2'] ...
 partition_spec:
       (partition_col = partition_col_value, partition_col = partiton_col_value, ...)

删除partitions：

 ALTER TABLE table_name DROP [IF EXISTS] partition_spec, partition_spec,...

示例：

 hive> create table alter_test(id INT, name STRING)
     > partitioned by(dt STRING)
     > row format delimited fields terminated by ',';
 OK
 Time taken: 0.259 seconds
 hive> create table alter_tmp(id INT, name STRING，dt STRING)
     > row format delimited fields terminated by ',';
 OK
 Time taken: 2.078 seconds
 hive> load data local inpath '/home/work/data/alter_test.txt' into table alter_tmp;
 Copying data from file:/home/work/data/alter_test.txt
 Copying file: file:/home/work/data/alter_test.txt
 Loading data to table default.alter_tmp
 OK
 Time taken: 2.71 seconds
 hive> set hive.exec.dynamic.partition.mode=nonstrict;
 hive> set hive.exec.dynamic.partition=true;
 hive> insert overwrite table alter_test partition(dt)
     > select id,name,dt
     > from alter_tmp;
 OK
 Time taken: 25.988 seconds
 $ cat alter_test2.txt
 1,zxm,2012-08-13
 2,ljz,2012-08-13
 $ hadoop fs -put alter_test2.txt /data/
 hive> alter table alter_test add partition(dt='2012-08-13') location '/data';
 OK
 Time taken: 8.717 seconds
 $ hadoop fs -ls /user/hive/warehouse/alter_test/
 Found 3 items
 drwxr-xr-x   - work supergroup          0 2012-08-12 20:50 /user/hive/warehouse/alter_test/dt=2012-08-10
 drwxr-xr-x   - work supergroup          0 2012-08-12 20:50 /user/hive/warehouse/alter_test/dt=2012-08-11
 drwxr-xr-x   - work supergroup          0 2012-08-12 20:50 /user/hive/warehouse/alter_test/dt=2012-08-12
 hive> select * from alter_test where dt='2012-08-13';
 OK
 1       zxm     2012-08-13
 2       ljz     2012-08-13
 Time taken: 6.064 seconds
 $ hadoop fs -rmr  /data
 hive> select * from alter_test where dt='2012-08-13';
 OK
 Time taken: 1.903 seconds
 hive> show partitions alter_test;
 OK
 dt=2012-08-10
 dt=2012-08-11
 dt=2012-08-12
 dt=2012-08-13
 Time taken: 0.546 seconds
 > alter table alter_test add partition(dt='2012-08-14') partition(dt='2012-08-15');
 OK
 Time taken: 0.57 seconds
 hive> alter table alter_test drop partition(dt='2012-08-10');
 Dropping the partition dt=2012-08-10
 OK
 Time taken: 4.509 seconds
 $ hadoop fs -ls /user/hive/warehouse/alter_test/
 Found 4 items
 drwxr-xr-x   - work supergroup          0 2012-08-12 20:50 /user/hive/warehouse/alter_test/dt=2012-08-11
 drwxr-xr-x   - work supergroup          0 2012-08-12 20:50 /user/hive/warehouse/alter_test/dt=2012-08-12
 drwxr-xr-x   - work supergroup          0 2012-08-13 02:15 /user/hive/warehouse/alter_test/dt=2012-08-14
 drwxr-xr-x   - work supergroup          0 2012-08-13 02:15 /user/hive/warehouse/alter_test/dt=2012-08-15

注意：
1. hive可以同时增加或者删除多个partition
2. 使用location关键字时，增加的partition以类似extend table数据的形式存在外部。

Alter Column
修改column属性（列名，列字段类型，列注释）：

 ALTER TABLE table_name
       CHANGE [COLUMN] col_old_name col_new_name
       column_type [COMMENT col_comment] [FIRST|AFTER column_name]

增加/替换column（可以使用replace来删除不需要的字段）：

 ALTER TABLE table_name
       ADD|REPLACE COLUMNS (col_name data_type [COMMENT col_comment], ...)

示例：

 hive> alter table alter_test add columns(test_columen INT);
 OK
 Time taken: 2.096 seconds
 hive> desc alter_test;
 OK
 id      int
 name    string
 test_columen    int
 dt      string
 Time taken: 0.345 seconds
 hive> select * from alter_test;
 OK
 3       cds     NULL    2012-08-11
 4       mac     NULL    2012-08-11
 1       zxm     NULL    2012-08-12
 2       ljz     NULL    2012-08-12
 1       zxm     NULL    2012-08-13
 2       ljz     NULL    2012-08-13
 Time taken: 8.467 seconds
 hive> alter table alter_test replace columns (id int, name string);
 OK
 Time taken: 0.217 seconds
 hive> desc alter_test;
 OK
 id      int
 name    string
 dt      string
 Time taken: 0.181 seconds
 hive> select * from alter_test;
 OK
 3       cds     2012-08-11
 4       mac     2012-08-11
 1       zxm     2012-08-12
 2       ljz     2012-08-12
 1       zxm     2012-08-13
 2       ljz     2012-08-13
 Time taken: 0.364 seconds
 hive> alter table alter_test change id myid INT;
 OK
 Time taken: 0.259 seconds
 hive> desc alter_test;
 OK
 myid    int
 name    string
 dt      string
 Time taken: 0.053 seconds

注意：column alter仅仅修改table的元数据，而不会修改数据。

其它：
hive alter语句还支持：
1.Alter Table Properties
2.Alter SerDe Properties
3.Alter Table/Partition File Format
4.Alter Table Storage Properties
5.Alter Table/Partition Location
6.Alter Table Touch
7.Alter Table (Un)Archive
8.Alter Table/Partition Protections
9.Alter Table Rename Partition

reference:
Hive LanguageManualDDL