Hive的锁有两个Lock方式
- Shared (S) 共享表
- Exclusive (X) 独享表、排他表
总结起来就是：
- 1）查询操作使用共享锁，共享锁是可以多重、并发使用的
- 2）修改表操作使用独占锁，它会阻止其他的查询、修改操作
- 3）可以对分区使用锁。
以下情况会出发锁，以及它的类型和锁定范围如下：
| Hive Command |
Locks Acquired |
|---|---|
| select .. T1 partition P1 |
S on T1, T1.P1 |
| insert into T2(partition P2) select .. T1 partition P1 |
S on T2, T1, T1.P1 and X on T2.P2 |
| insert into T2(partition P.Q) select .. T1 partition P1 |
S on T2, T2.P, T1, T1.P1 and X on T2.P.Q
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|
| alter table T1 rename T2 |
X on T1 |
| alter table T1 add cols |
X on T1 |
| alter table T1 replace cols |
X on T1 |
| alter table T1 change cols |
X on T1 |
| alter table T1 concatenate |
X on T1 |
| alter table T1 add partition P1 |
S on T1, X on T1.P1 |
| alter table T1 drop partition P1 |
S on T1, X on T1.P1 |
| alter table T1 touch partition P1 |
S on T1, X on T1.P1 |
| alter table T1 set serdeproperties |
S on T1 |
| alter table T1 set serializer |
S on T1 |
| alter table T1 set file format |
S on T1 |
| alter table T1 set tblproperties |
X on T1 |
| alter table T1 partition P1 concatenate |
X on T1.P1 |
| drop table T1 |
X on T1 |
对锁的操作Locks
show locks;
SHOW LOCKS <TABLE_NAME>;
SHOW LOCKS <TABLE_NAME> extended;
SHOW LOCKS <TABLE_NAME> PARTITION (<PARTITION_DESC>);
SHOW LOCKS <TABLE_NAME> PARTITION (<PARTITION_DESC>) extended;