Hadoop集群(五)Hive安装
作为一个多年的DBA，hadoop家族中，最亲切的产品就是hive了。毕竟SQL的使用还是很熟悉的。再也不用担心编写Mapreducer的痛苦了。
让客户满意是我们工作的目标，不断超越客户的期望值来自于我们对这个行业的热爱。我们立志把好的技术通过有效、简单的方式提供给客户，将通过不懈努力成为客户在信息化领域值得信任、有价值的长期合作伙伴，公司提供的服务项目有：空间域名、雅安服务器托管、营销软件、网站建设、新建网站维护、网站推广。
首先还是简单介绍一下Hive吧
Hive是基于Hadoop的数据仓库解决方案。由于Hadoop本身在数据存储和计算方面有很好的可扩展性和高容错性，因此使用Hive构建的数据仓库也秉承了这些特性。
简单来说，Hive就是在Hadoop上架了一层SQL接口，可以将SQL翻译成MapReduce去Hadoop上执行，这样就使得数据开发和分析人员很方便的使用SQL来完成海量数据的统计和分析，而不必使用编程语言开发MapReduce那么麻烦。
下面开始Hive的安装, 安装hive的前提，是hdfs，yarn已经安装完成并启动。hdfs安装，可以参考
Hadoop集群(一) Zookeeper搭建
Hadoop集群(二) HDFS搭建
Hadoop集群(三) Hbase搭建
Hive软件的下载，我使用版本是hive-1.2.1，现在已经无法下载了。大家可以根据需要下载新版本。
http://hive.apache.org/downloads.html
tar -xzvf apache-hive-1.2.1-bin.tar.gz- 修改hive-site.xml数据库相关的配置，主要有下面几个。实际生产中，还有很多其他的参数需要配置，比如后面提及的lzo压缩，kerberos等。这几个参数只是最基本保证hive运行的参数。
##javax.jdo.option.ConnectionURL，将该name对应的value修改为MySQL的地址，例如：javax.jdo.option.ConnectionURL jdbc:mysql://localhost:3306/hive?createDatabaseIfNotExist=true ##javax.jdo.option.ConnectionDriverName，将该name对应的value修改为MySQL驱动类路径，例如我的修改后是：javax.jdo.option.ConnectionDriverName com.mysql.jdbc.Driver javax.jdo.option.ConnectionUserName root ##javax.jdo.option.ConnectionPassword，将对应的value修改为MySQL数据库的登录密码：javax.jdo.option.ConnectionPassword change to your password ##hive.metastore.schema.verification，将对应的value修改为false：hive.metastore.schema.verification false 创建对应目录
mkdir -p /data1/hiveLogs-security/;chown -R hive:hadoop /data1/hiveLogs-security/ mkdir -p /data1/hiveData-security/;chown -R hive:hadoop /data1/hiveData-security/ mkdir -p /tmp/hive-security/operation_logs; chown -R hive:hadoop /tmp/hive-security/operation_logs创建hdfs目录
hadoop fs -mkdir /tmp hadoop fs -mkdir -p /user/hive/warehouse hadoop fs -chmod g+w /tmp hadoop fs -chmod g+w /user/hive/warehouse初始化hive
[hive@aznbhivel01 ~]$ schematool -initSchema -dbType mysql Metastore connection URL: jdbc:mysql://172.16.13.88:3306/hive_beta?useUnicode=true&characterEncoding=UTF-8&createDatabaseIfNotExist=true Metastore Connection Driver : com.mysql.jdbc.Driver Metastore connection User: envision Starting metastore schema initialization to 1.2.0 Initialization script hive-schema-1.2.0.mysql.sql Initialization script completed schemaTool completed- 第一次启动hive，遇到错误，其实很多错误，都是一个“hive小白” 意识不到的配置问题，和启动等问题。对于老司机，这些都不是问题。
原因：因为没有正常启动Hive 的 Metastore Server服务进程。
[hive@aznbhivel01 ~]$ hive
Logging initialized using configuration in file:/usr/local/hadoop/apache-hive-1.2.1/conf/hive-log4j.properties
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:528)
at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:677)
at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:621)
......
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.apache.hadoop.hive.metastore.MetaStoreUtils.newInstance(MetaStoreUtils.java:1521)
... 14 more
Caused by: MetaException(message:Could not connect to meta store using any of the URIs provided. Most recent failure: ···
-7. 解决方法：启动Hive 的 Metastore Server服务进程，执行如下命令,，遇到下一个问题
[hive@aznbhivel01 ~]$ Starting Hive Metastore Server
hiveorg.apache.thrift.transport.TTransportException: java.io.IOException: Login failure for hive/aznbhivel01.liang.com@ENVISIONCN.COM from keytab /etc/security/keytab/hive.keytab: javax.security.auth.login.LoginException: Unable to obtain password from user
at org.apache.hadoop.hive.thrift.HadoopThriftAuthBridge$Server.
at org.apache.hadoop.hive.thrift.HadoopThriftAuthBridge.createServer(HadoopThriftAuthBridge.java:102)
at org.apache.hadoop.hive.metastore.HiveMetaStore.startMetaStore(HiveMetaStore.java:5990)
at org.apache.hadoop.hive.metastore.HiveMetaStore.main(HiveMetaStore.java:5909)
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.io.IOException: Login failure for hive/aznbhivel01.liang.com@ENVISIONCN.COM from keytab /etc/security/keytab/hive.keytab: javax.security.auth.login.LoginException: Unable to obtain password from user```
-8. keytab 没找到，修正hive.keytab文件权限问题。
$ ll /etc/security/keytab/
total 100
-r-------- 1 hbase hadoop 18002 Dec 5 17:06 hbase.keytab
-r-------- 1 hdfs hadoop 18002 Dec 5 17:04 hdfs.keytab
-r-------- 1 hive hadoop 18002 Dec 5 17:06 hive.keytab
-r-------- 1 mapred hadoop 18002 Dec 5 17:06 mapred.keytab
-r-------- 1 yarn hadoop 18002 Dec 5 17:06 yarn.keytab-9. 再次重启metastore
$ hive --service metastore &
[2] 41285
[1] Killed hive --service metastore (wd: ~)
(wd now: /etc/security)
[hive@aznbhivel01 security]$ Starting Hive Metastore Server-10. 然后启动hiveserverhive --service hiveserver2 &
-11. 启动依然失败，很困惑。问题很明显，就是说kerberos的KDC中无法找到这个server。但是已经kinit并且成功了。而且日志前面也说了，认证成功。
尝试重新生成keytab也无效。最后考虑是不是hive-site.xml中写的是IP的原因？修改成主机名，这个问题解决“thrift://aznbhivel01.liang.com:9083”
~~~~需要修改的配置文件信息~~~
hive.metastore.uris
thrift://aznbhivel01.liang.com:9083
Thrift URI for the remote metastore. Used by metastore client to connect to remote metastore. ~~~~~~~~~log信息~~~~~~
2017-12-07 16:16:04,300 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:login(221)) - hadoop login
2017-12-07 16:16:04,302 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:commit(156)) - hadoop login commit
2017-12-07 16:16:04,303 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:commit(170)) - using kerberos user:hive/aznbhivel01.liang.com@LIANG.COM
2017-12-07 16:16:04,303 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:commit(192)) - Using user: "hive/aznbhivel01.liang.com@LIANG.COM" with name hive/aznbhivel01.liang.com@LIANG.COM
2017-12-07 16:16:04,303 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:commit(202)) - User entry: "hive/aznbhivel01.liang.com@LIANG.COM"
2017-12-07 16:16:04,304 INFO [main]: security.UserGroupInformation (UserGroupInformation.java:loginUserFromKeytab(965)) - Login successful for user hive/aznbhivel01.liang.com@LIANG.COM using keytab file /etc/security/keytab/hive.keytab
........
Client Addresses Null
2017-12-07 16:16:04,408 INFO [main]: hive.metastore (HiveMetaStoreClient.java:open(386)) - Trying to connect to metastore with URI thrift://172.16.13.88:9083
2017-12-07 16:16:04,446 DEBUG [main]: security.UserGroupInformation (UserGroupInformation.java:logPrivilegedAction(1681)) - PrivilegedAction as:hive/aznbhivel01.liang.com@LIANG.COM (auth:KERBEROS) from:org.apache.hadoop.hive.thrift.client.TUGIAssumingTransport.open(TUGIAssumingTransport.java:49)
2017-12-07 16:16:04,448 DEBUG [main]: transport.TSaslTransport (TSaslTransport.java:open(261)) - opening transport org.apache.thrift.transport.TSaslClientTransport@5bb4d6c0
2017-12-07 16:16:04,460 ERROR [main]: transport.TSaslTransport (TSaslTransport.java:open(315)) - SASL negotiation failure
javax.security.sasl.SaslException: GSS initiate failed [Caused by GSSException: No valid credentials provided (Mechanism level: Server not found in Kerberos database (7) - UNKNOWN_SERVER)]
at com.sun.security.sasl.gsskerb.GssKrb5Client.evaluateChallenge(GssKrb5Client.java:212)
at org.apache.thrift.transport.TSaslClientTransport.handleSaslStartMessage(TSaslClientTransport.java:94)-12. 然后又遇到权限错误，他也不是哪里权限不对。hdfs已经可以看到hive写入的文件了，权限应该正确。继续分析.....
2017-12-07 20:30:59,168 DEBUG [IPC Client (1612726596) connection to AZcbetannL02.liang.com/172.16.13.77:9000 from hive/aznbhivel01.liang.com@LIANG.COM]: ipc.Client (Client.java:receiveRpcResponse(1089)) - IPC Client (1612726596) connection to AZcbetannL02.liang.com/172.16.13.77:9000 from hive/aznbhivel01.liang.com@LIANG.COM got value #8
2017-12-07 20:30:59,168 DEBUG [main]: ipc.ProtobufRpcEngine (ProtobufRpcEngine.java:invoke(250)) - Call: getFileInfo took 2ms
2017-12-07 20:30:59,168 INFO [main]: server.HiveServer2 (HiveServer2.java:stop(305)) - Shutting down HiveServer2
2017-12-07 20:30:59,169 INFO [main]: server.HiveServer2 (HiveServer2.java:startHiveServer2(368)) - Exception caught when calling stop of HiveServer2 before retrying start
java.lang.NullPointerException
at org.apache.hive.service.server.HiveServer2.stop(HiveServer2.java:309)
at org.apache.hive.service.server.HiveServer2.startHiveServer2(HiveServer2.java:366)
at org.apache.hive.service.server.HiveServer2.access$700(HiveServer2.java:74)
at org.apache.hive.service.server.HiveServer2$StartOptionExecutor.execute(HiveServer2.java:588)
at org.apache.hive.service.server.HiveServer2.main(HiveServer2.java:461)
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)
2017-12-07 20:30:59,170 WARN [main]: server.HiveServer2 (HiveServer2.java:startHiveServer2(376)) - Error starting HiveServer2 on attempt 1, will retry in 60 seconds
java.lang.RuntimeException: Error applying authorization policy on hive configuration: java.lang.RuntimeException: java.io.IOException: Permission denied
at org.apache.hive.service.cli.CLIService.init(CLIService.java:114)
at org.apache.hive.service.CompositeService.init(CompositeService.java:59)
at org.apache.hive.service.server.HiveServer2.init(HiveServer2.java:100)
at org.apache.hive.service.server.HiveServer2.startHiveServer2(HiveServer2.java:345)
at org.apache.hive.service.server.HiveServer2.access$700(HiveServer2.java:74)
at org.apache.hive.service.server.HiveServer2$StartOptionExecutor.execute(HiveServer2.java:588)
at org.apache.hive.service.server.HiveServer2.main(HiveServer2.java:461)
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: java.lang.RuntimeException: java.io.IOException: Permission denied
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:528)
at org.apache.hive.service.cli.CLIService.applyAuthorizationConfigPolicy(CLIService.java:127)
at org.apache.hive.service.cli.CLIService.init(CLIService.java:112)
... 12 more
Caused by: java.lang.RuntimeException: java.io.IOException: Permission denied
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:521)
... 14 more
Caused by: java.io.IOException: Permission denied
at java.io.UnixFileSystem.createFileExclusively(Native Method)
at java.io.File.createNewFile(File.java:1006)
at java.io.File.createTempFile(File.java:1989)
at org.apache.hadoop.hive.ql.session.SessionState.createTempFile(SessionState.java:824)
at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:519)
... 14 moreGoogle到的strace方法，看是什么权限问题
strace is your friend if you are on Linux. Try the following from the
shell in which you are starting hive...
strace -f -e trace=file service hive-server2 start 2>&1 | grep ermission
You should see the file it can't read/write.
上面的问题，最后发现 /tmp/hive-security路径的权限不对，修改之后，这个问题过去了。
hive.exec.local.scratchdir
/tmp/hive-security -13. 下一个问题，继续：
2017-12-07 20:58:56,749 DEBUG [IPC Parameter Sending Thread #0]: ipc.Client (Client.java:run(1032)) - IPC Client (1612726596) connection to AZcbetannL02.liang.com/172.16.13.77:9000 from hive/aznbhivel01.liang.com@LIANG.COM sending #8
2017-12-07 20:58:56,750 DEBUG [IPC Client (1612726596) connection to AZcbetannL02.liang.com/172.16.13.77:9000 from hive/aznbhivel01.liang.com@LIANG.COM]: ipc.Client (Client.java:receiveRpcResponse(1089)) - IPC Client (1612726596) connection to AZcbetannL02.liang.com/172.16.13.77:9000 from hive/aznbhivel01.liang.com@LIANG.COM got value #8
2017-12-07 20:58:56,750 DEBUG [main]: ipc.ProtobufRpcEngine (ProtobufRpcEngine.java:invoke(250)) - Call: getFileInfo took 2ms
2017-12-07 20:58:56,763 ERROR [main]: session.SessionState (SessionState.java:setupAuth(749)) - Error setting up authorization: java.lang.ClassNotFoundException: org.apache.ranger.authorization.hive.authorizer.RangerHiveAuthorizerFactory
org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassNotFoundException: org.apache.ranger.authorization.hive.authorizer.RangerHiveAuthorizerFactory
at org.apache.hadoop.hive.ql.metadata.HiveUtils.getAuthorizeProviderManager(HiveUtils.java:391)google查询关键字org.apache.ranger.authorization.hive.authorizer.RangerHiveAuthorizerFactory
找到文章
https://www.cnblogs.com/wyl9527/p/6835620.html
执行启动命令后需要进行重启hive服务.
安装结束后：
会看见多了几个配置文件。
修改hiveserver2-site.xml 文件
hive.security.authorization.enabled
true
hive.security.authorization.manager
org.apache.ranger.authorization.hive.authorizer.RangerHiveAuthorizerFactory
hive.security.authenticator.manager
org.apache.hadoop.hive.ql.security.SessionStateUserAuthenticator
hive.conf.restricted.list
hive.security.authorization.enabled,hive.security.authorization.manager,hive.security.authenticator.manager
目前没有使用ranger安全认证，决定取消它。怎么取消呢？
干脆删除hiveserver2-site.xml 文件。又向前爬了一步， hiveserver2启动成功了。hive进去了，遇到下一个错误。
-14. 可以正常启动hive了，也可以通过hive命令进入查询，但是可以看到，命令执行是OK的，但是不能正常返回查询结果
[hive@aznbhivel01 hive]$ hive
Logging initialized using configuration in file:/usr/local/hadoop/apache-hive-1.2.1/conf/hive-log4j.properties
hive> show databases;
OK
Failed with exception java.io.IOException:java.lang.RuntimeException: Error in configuring object
Time taken: 0.867 seconds 百度解决方法
http://blog.csdn.net/wodedipang_/article/details/72720257
但是我的配置是，没有文中说到的情况。怀疑是这个文件夹的权限等问题
hive.exec.local.scratchdir
/tmp/hive-security
Local scratch space for Hive jobs
最后在日志hive.log中有如下错误，说明缺少jar包
Caused by: java.lang.IllegalArgumentException: Compression codec com.hadoop.compression.lzo.LzoCodec not found.
at org.apache.hadoop.io.compress.CompressionCodecFactory.getCodecClasses(CompressionCodecFactory.java:139)
at org.apache.hadoop.io.compress.CompressionCodecFactory.(CompressionCodecFactory.java:179)
at org.apache.hadoop.mapred.TextInputFormat.configure(TextInputFormat.java:45)
... 26 more
Caused by: java.lang.ClassNotFoundException: Class com.hadoop.compression.lzo.LzoCodec not found
at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:2101)
at org.apache.hadoop.io.compress.CompressionCodecFactory.getCodecClasses(CompressionCodecFactory.java:132)
... 28 more -15. 是hadoop的core-site.xml中有设置，有设置lzo.LzoCodec的压缩方式，所以需要对应的jar包支持，才能正常执行Mapreducer
io.compression.codecs org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec,com.hadoop.compression.lzo.LzoCodec,org.apache.hadoop.io.compress.SnappyCodec,com.hadoop.compression.lzo.LzopCodec
io.compression.codec.lzo.class
com.hadoop.compression.lzo.LzoCodec
hadoop.http.staticuser.user
hadoop
lzo.text.input.format.ignore.nonlzo
false 将需要的包，从其他正常的环境copy过来，解决了。
注意，lzo jar包不只是在hive服务器上，在全部的yarn/MapReduce机器上，都需要有这个jar包，不然在调用mapreduce过程中，涉及到lzo压缩的话，就会出问题，而不只是hive发起的任务会遇到问题。
# pwd
/usr/local/hadoop/hadoop-release/share/hadoop/common
# ls |grep lzo
hadoop-lzo-0.4.21-SNAPSHOT.jar至此，hive安装完成了。
爬过一个有一个坑，来感受一下hive查询的输出吧：
hive> select count(*) from test.testxx;
Query ID = hive_20171224121853_d96ed531-7e09-438d-b383-bc2a715753fc
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks determined at compile time: 1
Starting Job = job_1513915190261_0008, Tracking URL = https://aznbrmnl02.liang.com:8089/proxy/application_1513915190261_0008/
Kill Command = /usr/local/hadoop/hadoop-2.7.1/bin/hadoop job -kill job_1513915190261_0008
Hadoop job information for Stage-1: number of mappers: 3; number of reducers: 1
2017-12-24 12:19:11,332 Stage-1 map = 0%, reduce = 0%
2017-12-24 12:19:19,666 Stage-1 map = 100%, reduce = 0%, Cumulative CPU 3.85 sec
2017-12-24 12:19:30,064 Stage-1 map = 100%, reduce = 100%, Cumulative CPU 5.43 sec
MapReduce Total cumulative CPU time: 5 seconds 430 msec
Ended Job = job_1513915190261_0008
MapReduce Jobs Launched:
Stage-Stage-1: Map: 3 Reduce: 1 Cumulative CPU: 5.43 sec HDFS Read: 32145 HDFS Write: 5 SUCCESS
Total MapReduce CPU Time Spent: 5 seconds 430 msec
OK
2526
Time taken: 38.834 seconds, Fetched: 1 row(s)需要注意的点
-1. mysql的字符集是latin1，这个字符集在安装hive的时候是适合的，但是后面使用的时候，尤其有中午文件存入的时候，就会无法正常显示。所以建议，安装完hive之后，修改字符集到UTF8
mysql> SHOW VARIABLES LIKE 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)-2修改字符集
-# vi /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
default-character-set = utf8
character_set_server = utf8
-# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid-3修改后
mysql> SHOW VARIABLES LIKE 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)连接hive的方式
a. hive直接连接的方式，如果有kerberos，注意先kinit认证
su - hive
hiveb. beeline连接beeline -u "jdbc:hive2://hive-hostname:10000/default;principal=hive/_HOST@LIANG.COM"
如果是hiveserver2 HA的架构，连接方式如下：beeline -u "jdbc:hive2://zookeeper1-ip:2181,zookeeper2-ip:2181,zookeeper3-ip:2181/;serviceDiscoveryMode=zooKeeper;zooKeeperNamespace=hiveserver2_zk;principal=hive/_HOST@LIANG.COM"
如果没有kerberos等安全认证的情况下，beeline连接hive，需要指明登陆的用户。
beeline -u "jdbc:hive2://127.0.0.1:10000/default;" -n hive
另外，Hive在执行过程中，是否会走mapreducer？
hive 0.10.0为了执行效率考虑，简单的查询，就是只是select，不带count,sum,group by这样的，都不走map/reduce，直接读取hdfs文件进行filter过滤。这样做的好处就是不新开mr任务，执行效率要提高不少，但是不好的 地方就是用户界面不友好，有时候数据量大还是要等很长时间，但是又没有任何返回。
改这个很简单，在hive-site.xml里面有个配置参数叫
hive.fetch.task.conversion
将这个参数设置为more，简单查询就不走map/reduce了，设置为minimal，就任何简单select都会走map/reduce
----Update 2018.2.11-----
如果重新初始化hive的mysql库，需要先登陆mysql，drop原有的库，不然会遇到下面错误
-# su - hive
[hive@aznbhivel01 ~]$ schematool -initSchema -dbType mysql
Metastore connection URL: jdbc:mysql://10.24.101.88:3306/hive_beta?useUnicode=true&characterEncoding=UTF-8&createDatabaseIfNotExist=true
Metastore Connection Driver : com.mysql.jdbc.Driver
Metastore connection User: envision
Starting metastore schema initialization to 1.2.0
Initialization script hive-schema-1.2.0.mysql.sql
Error: Specified key was too long; max key length is 3072 bytes (state=42000,code=1071)
org.apache.hadoop.hive.metastore.HiveMetaException: Schema initialization FAILED! Metastore state would be inconsistent !!
schemaTool failed
删除原有hive库之后，再次初始化，就直接OK了
[hive@aznbhivel01 ~]$ schematool -initSchema -dbType mysql
Metastore connection URL: jdbc:mysql://10.24.101.88:3306/hive_beta?useUnicode=true&characterEncoding=UTF-8&createDatabaseIfNotExist=true
Metastore Connection Driver : com.mysql.jdbc.Driver
Metastore connection User: envision
Starting metastore schema initialization to 1.2.0
Initialization script hive-schema-1.2.0.mysql.sql
Initialization script completed
schemaTool completed
Hive的启动与关闭：
1.启动metastore
nohup /usr/local/hadoop/hive-release/bin/hive --service metastore --hiveconf hive.log4j.file=/usr/local/hadoop/hive-release/conf/meta-log4j.properties > /data1/hiveLogs-security/metastore.log 2>&1 &
2.启动hiveserver2
nohup /usr/local/hadoop/hive-release/bin/hive --service hiveserver2 > /data1/hiveLogs-security/hiveserver2.log 2>&1 &
3.关闭HiveServer2kill -9ps ax --cols 2000 | grep java | grep HiveServer2 | grep -v 'ps ax' | awk '{print $1;}'``
4.关闭metastorekill -9ps ax --cols 2000 | grep java | grep MetaStore | grep -v 'ps ax' | awk '{print $1;}'``
本文标题：Hadoop集群(五)Hive安装
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