使用sqoop将表从RDBMS导入HIVE后是否仍然存在约束？

Question

当我们使用sqoop import将RDBMS表传输到HIVE时，表的约束如主键是否仍然存在？

即，作为主键的表的列是否仍然是HIVE的主键。这些信息会在Hive Metastore中吗？

非常感谢。

Answer 1

正如您在下面的Hive QL官方文档的链接中所看到的，自Hive版本2.1.0以来已添加了PRIMARY和FOREIGN约束。 Hive QL

因此，我假设使用sqoop将表导入Hive时，PRIMARY和FOREIGN Keys约束将保留。

我测试了一个sqoop导入的MySQL数据库，我可以看到在导入过程中没有维护PRIMARY KEY CONSTRAINT。

MySQL表格式：

    mysql> show create table employees;
+-----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table     | Create Table                                                                                                                                                                                                                                                                                   |
+-----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| employees | CREATE TABLE `employees` (
  `emp_no` int(11) NOT NULL,
  `birth_date` date NOT NULL,
  `first_name` varchar(14) NOT NULL,
  `last_name` varchar(16) NOT NULL,
  `gender` enum('M','F') NOT NULL,
  `hire_date` date NOT NULL,
  PRIMARY KEY (`emp_no`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0,00 sec)

使用以下命令将数据从MySQL导入到Hive：

sqoop import --connect jdbc:mysql://localhost/employees --username root --password password --table employees --hive-import --create-hive-table --hive-table employees

当我在hive中描述表时，我看不到PRIMARY KEY CONSTRAINT

hive> show create table employees;
OK
CREATE TABLE `employees`(
  `emp_no` int, 
  `birth_date` string, 
  `first_name` string, 
  `last_name` string, 
  `gender` string, 
  `hire_date` string)
COMMENT 'Imported by sqoop on 2019/03/18 00:24:11'
ROW FORMAT SERDE 
  'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe' 
WITH SERDEPROPERTIES ( 
  'field.delim'='', 
  'line.delim'='\n', 
  'serialization.format'='') 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.mapred.TextInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION
  'hdfs://localhost:9000/user/hive/warehouse/employees'
TBLPROPERTIES (
  'transient_lastDdlTime'='1552865076')
Time taken: 1.304 seconds, Fetched: 22 row(s)

我插入了一个具有相同员工编号的新行，以检查Hive是否管理PK约束。如您所见，新行已添加：

hive> insert into employees values (10001, "1986-04-17", "Hichem", 
"BOUSSETTA", "M", "2014-09-91");
Moving data to directory hdfs://localhost:9000/user/hive/warehouse/employees/.hive-staging_hive_2019-03-18_00-32-16_851_8569619447966100947-1/-ext-10000
Loading data to table default.employees
MapReduce Jobs Launched: 
Stage-Stage-1: Map: 1   Cumulative CPU: 5.79 sec   HDFS Read: 5080 HDFS Write: 120 SUCCESS
Total MapReduce CPU Time Spent: 5 seconds 790 msec
OK
Time taken: 42.422 seconds
hive> select * from employees;
OK
10001   1986-04-17  Hichem  BOUSSETTA   M   2014-09-91
10001   1953-09-02  Georgi  Facello M   1986-06-26
10002   1964-06-02  Bezalel Simmel  F   1985-11-21

总结一下：在将RDBMS数据导入Hive时，Sqoop不保留PK约束