Hive导入文件案例

1需求

将本地/opt/module/datas/student.txt 这个目录下的数据导入到 hive 的 student(id int, name string)表中。

数据准备
- 在/opt/module/datas 这个目录下准备数据
  - 在/opt/module/目录下创建 datas mkdir datas
  - 在/opt/module/datas/目录下创建 student.txt 文件并添加数据
```
touch student.txt 
vi student.txt 
1001 zhangshan 
1002 lishi 
1003 zhaoliu
```
    注意以 tab 键间隔
Hive 实际操作
- 启动 hive bin/hive
- 显示数据库 hive> show databases;
- 使用 default 数据库 hive> use default;
- 显示 default 数据库中的表 hive> show tables;
- 删除已创建的 student 表 hive> drop table student;
- 创建 student 表, 并声明文件分隔符’\t’ hive> create table student(id int, name string) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t';
- 加载/opt/module/datas/student.txt 文件到 student 数据库表中。
  
  hive> load data local inpath '/opt/module/datas/student.txt' into table student;
- Hive 查询结果
```
hive> select * from student; 
OK
1001 zhangshan 
1002 lishi 
1003 zhaoliu 
Time taken: 0.266 seconds,Fetched: 3 row(s)
```

遇到的问题

再打开一个客户端窗口启动 hive，会产生 java.sql.SQLException 异常。

Exception in thread "main" java.lang.RuntimeException: java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:522) at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:677) at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:621) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java: 43) at java.lang.reflect.Method.invoke(Method.java:606) at org.apache.hadoop.util.RunJar.run(RunJar.java:221) at org.apache.hadoop.util.RunJar.main(RunJar.java:136) Caused by: java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient at org.apache.hadoop.hive.metastore.MetaStoreUtils.newInstance(MetaStoreUtils.java:1 523) at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.<init>(RetryingMetaStore Client.java:86) at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaSto reClient.java:132) at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.getProxy(RetryingMetaSto reClient.java:104) at org.apache.hadoop.hive.ql.metadata.Hive.createMetaStoreClient(Hive.java:3005) at org.apache.hadoop.hive.ql.metadata.Hive.getMSC(Hive.java:3024) at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:503) ... 8 more

原因是，Metastore 默认存储在自带的 derby 数据库中(只允许一个连接)，推荐使用 MySQL 存储 Metastore;