Question

使用外部配置单元表时，是否可以删除目录中的数据，但通过查询保留分区。请注意我不想放弃桌子并重新创建它。我只是想清空底层文件夹并重新开始一个进程。我的表很大，按年，月，日和小时分区，手动重新创建分区需要花费大量时间。

由于

Answer 1

truncate table ...删除所有数据 truncate table partition (...)删除特定分区的数据。

保留目录结构。

外部表应首先转换为manged，.e.g

alter table t set tblproperties('EXTERNAL'='FALSE');

当我们完成后，我们可以将其转换回来

alter table t set tblproperties('EXTERNAL'='TRUE');

演示

create table t (i int) partitioned by (x char(1));
set hive.exec.dynamic.partition.mode=nonstrict;
insert into t partition (x) values (1,'A'),(2,'B'),(3,'C');
alter table t set tblproperties('EXTERNAL'='TRUE');

select * from t;

+-----+-----+
| t.i | t.x |
+-----+-----+
|   1 | A   |
|   2 | B   |
|   3 | C   |
+-----+-----+

dfs -ls -R /user/hive/warehouse/t;

drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:40 /user/hive/warehouse/t/x=A
-rwxrwxrwx   1 cloudera supergroup          2 2017-03-28 11:40 /user/hive/warehouse/t/x=A/000000_0
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:40 /user/hive/warehouse/t/x=B
-rwxrwxrwx   1 cloudera supergroup          2 2017-03-28 11:40 /user/hive/warehouse/t/x=B/000000_0
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:40 /user/hive/warehouse/t/x=C
-rwxrwxrwx   1 cloudera supergroup          2 2017-03-28 11:40 /user/hive/warehouse/t/x=C/000000_0

truncate table t partition (x='B');

FAILED：SemanticException [错误10146]：无法截断非托管表t。

alter table t set tblproperties('EXTERNAL'='FALSE');

truncate table t partition (x='B');

select * from t;

+-----+-----+
| t.i | t.x |
+-----+-----+
|   1 | A   |
|   3 | C   |
+-----+-----+

dfs -ls -R /user/hive/warehouse/t;

drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:40 /user/hive/warehouse/t/x=A
-rwxrwxrwx   1 cloudera supergroup          2 2017-03-28 11:40 /user/hive/warehouse/t/x=A/000000_0
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:42 /user/hive/warehouse/t/x=B
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:40 /user/hive/warehouse/t/x=C
-rwxrwxrwx   1 cloudera supergroup          2 2017-03-28 11:40 /user/hive/warehouse/t/x=C/000000_0

truncate table t;

+-----+-----+
| t.i | t.x |
+-----+-----+

dfs -ls -R /user/hive/warehouse/t;

drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:43 /user/hive/warehouse/t/x=A
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:43 /user/hive/warehouse/t/x=B
drwxrwxrwx   - cloudera supergroup          0 2017-03-28 11:43 /user/hive/warehouse/t/x=C

alter table t set tblproperties('EXTERNAL'='TRUE');

删除hive分区外部表但保留分区

1 个答案:

演示