大数据学习（8）Hive基础

什么是Hive

Hive是一个基于HDFS的查询引擎。我们日常中的需求如果都自己去写MapReduce来实现的话会很费劲的，Hive把日常用到的MapReduce功能，比如排序、分组等功能进行了抽象，对外提供类似于普通数据库的查询服务。

它只是封装MapReduce计算，但它本质并不是数据库服务，不适合作为联机服务。通常用于数据仓库的离线计算中。
在Hive中已经明确说明，不建议使用MapReduce了，而推荐使用Spark。

安装

tar -zxvf apache-hive-1.2.2-bin.tar.gz -C /usr/local/

hive-site.xml:

<configuration>
<property>
<name>javax.jdo.option.ConnectionURL</name>
<value>jdbc:mysql://localhost/hive_metastore?createDatabaseIfNotExist=true</value>
<description>metadata is stored in a MySQL server</description>
</property>
<property>
<name>javax.jdo.option.ConnectionDriverName</name>
<value>com.mysql.jdbc.Driver</value>
<description>MySQL JDBC driver class</description>
</property>
<property>
<name>javax.jdo.option.ConnectionUserName</name>
<value>root</value>
<description>user name for connecting to mysql server</description>
</property>
<property>
<name>javax.jdo.option.ConnectionPassword</name>
<value>root</value>
<description>password for connecting to mysql server</description>
</property>
</configuration>

拷贝MySQL驱动jar到hive的lib目录中。

先启动HDFS：

start-dfs.sh

再启动hive

如果报错:

Logging initialized using configuration in jar:file:/usr/local/apache-hive-1.2.2-bin/lib/hive-common-1.2.2.jar!/hive-log4j.properties
[ERROR] Terminal initialization failed; falling back to unsupported
java.lang.IncompatibleClassChangeError: Found class jline.Terminal, but interface was expected
at jline.TerminalFactory.create(TerminalFactory.java:101)
at jline.TerminalFactory.get(TerminalFactory.java:158)
at jline.console.ConsoleReader.<init>(ConsoleReader.java:229)
at jline.console.ConsoleReader.<init>(ConsoleReader.java:221)
at jline.console.ConsoleReader.<init>(ConsoleReader.java:209)
at org.apache.hadoop.hive.cli.CliDriver.setupConsoleReader(CliDriver.java:787)
at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:721)
at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:681)
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)

Exception in thread "main" java.lang.IncompatibleClassChangeError: Found class jline.Terminal, but interface was expected
at jline.console.ConsoleReader.<init>(ConsoleReader.java:230)
at jline.console.ConsoleReader.<init>(ConsoleReader.java:221)
at jline.console.ConsoleReader.<init>(ConsoleReader.java:209)
at org.apache.hadoop.hive.cli.CliDriver.setupConsoleReader(CliDriver.java:787)
at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:721)
at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:681)
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)

需要把hive下lib目录中的jline jar文件替换到hadoop中yarn目录中：

rm /usr/local/hadoop-2.6.5/share/hadoop/yarn/lib/jline-0.9.94.jar 
cp /usr/local/apache-hive-1.2.2-bin/lib/jline-2.12.jar /usr/local/hadoop-2.6.5/share/hadoop/yarn/lib/

启动之后会自动创建数据库，登录数据库中可以查看到一些元信息：

mysql> use hive_metastore;
mysql> use hive_metastore ;
mysql> select * from dbs;
+-------+-----------------------+------------------------------------------+---------+------------+------------+
| DB_ID | DESC | DB_LOCATION_URI | NAME | OWNER_NAME | OWNER_TYPE |
+-------+-----------------------+------------------------------------------+---------+------------+------------+
| 1 | Default Hive database | hdfs://centos01:9000/user/hive/warehouse | default | public | ROLE |
+-------+-----------------------+------------------------------------------+---------+------------+------------+
1 row in set (0.00 sec)

Hive基本操作

DDL
CREATE [EXTERNAL] TABLE [IF NOT EXISTS] table_name
[(col_name data_type [COMMENT col_comment], ...)]
[COMMENT table_comment]
[PARTITIONED BY (col_name data_type [COMMENT col_comment], ...)]
[CLUSTERED BY (col_name, col_name, ...)
[SORTED BY (col_name [ASC|DESC], ...)] INTO num_buckets BUCKETS]
[ROW FORMAT row_format]
[STORED AS file_format]
[LOCATION hdfs_path]
参考：https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL

Thrift

启动hiveserver2服务

./hiveserver2

使用beeline连接到这个服务上：

[root@centos01 bin]# ./beeline 
Beeline version 1.2.2 by Apache Hive
beeline> !connect jdbc:hive2://localhost:10000
Connecting to jdbc:hive2://localhost:10000
Enter username for jdbc:hive2://localhost:10000: root
Enter password for jdbc:hive2://localhost:10000: ****
Connected to: Apache Hive (version 1.2.2)
Driver: Hive JDBC (version 1.2.2)
Transaction isolation: TRANSACTION_REPEATABLE_READ
0: jdbc:hive2://localhost:10000> show databases;
+----------------+--+
| database_name |
+----------------+--+
| default |
+----------------+--+
1 row selected (3.666 seconds)
0: jdbc:hive2://localhost:10000>