lzo的安装及在hadoop中的配置
<property> <name>io.compression.codecs</name> <value>org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.DefaultCodec,com.hadoop.compression.lzo.LzoCodec,com.hadoop.compression.lzo.LzopCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property><property> <name>io.compression.codec.lzo.class</name> <value>com.hadoop.compression.lzo.LzoCodec</value></property>

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vi mapred-site.xml

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<property> <name>mapred.compress.map.output</name> <value>true</value> </property> <property> <name>mapred.map.output.compression.codec</name> <value>com.hadoop.compression.lzo.LzoCodec</value> </property>

以上在hadoop-0.20.203.0中测试通过，但在204.0和205.0中会出现如下问题：

hadoop-0.20.204.0中报错：

2012-01-06 12:09:30,475 ERROR lzo.GPLNativeCodeLoader (GPLNativeCodeLoader.java:<clinit>(36)) - Could not load native gpl library
java.lang.UnsatisfiedLinkError: no gplcompression in java.library.path
??????? at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1734)
??????? at java.lang.Runtime.loadLibrary0(Runtime.java:823)
??????? at java.lang.System.loadLibrary(System.java:1028)
??????? at com.hadoop.compression.lzo.GPLNativeCodeLoader.<clinit>(GPLNativeCodeLoader.java:32)
??????? at com.hadoop.compression.lzo.LzoCodec.<clinit>(LzoCodec.java:67)
??????? at java.lang.Class.forName0(Native Method)
??????? at java.lang.Class.forName(Class.java:247)
??????? at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:819)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.init(RCFile.java:1109)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.<init>(RCFile.java:983)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.<init>(RCFile.java:964)
??????? at org.apache.hadoop.hive.ql.io.RCFileRecordReader.<init>(RCFileRecordReader.java:52)
??????? at org.apache.hadoop.hive.ql.io.RCFileInputFormat.getRecordReader(RCFileInputFormat.java:57)
??????? at org.apache.hadoop.hive.ql.exec.FetchOperator.getRecordReader(FetchOperator.java:306)
??????? at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:320)
??????? at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:133)
??????? at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:1114)
??????? at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:187)
??????? at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:241)
??????? at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:456)
??????? at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
??????? at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
??????? at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
??????? at java.lang.reflect.Method.invoke(Method.java:597)
??????? at org.apache.hadoop.util.RunJar.main(RunJar.java:156)
2012-01-06 12:09:30,476 ERROR lzo.LzoCodec (LzoCodec.java:<clinit>(77)) - Cannot load native-lzo without native-hadoop
2012-01-06 12:09:30,478 ERROR CliDriver (SessionState.java:printError(343)) - Failed with exception java.io.IOException:java.lang.RuntimeException: native-lzo library not available
java.io.IOException: java.lang.RuntimeException: native-lzo library not available
??????? at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:341)
??????? at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:133)
??????? at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:1114)
??????? at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:187)
??????? at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:241)
??????? at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:456)
??????? at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
??????? at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
??????? at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
??????? at java.lang.reflect.Method.invoke(Method.java:597)
??????? at org.apache.hadoop.util.RunJar.main(RunJar.java:156)
Caused by: java.lang.RuntimeException: native-lzo library not available
??????? at com.hadoop.compression.lzo.LzoCodec.getDecompressorType(LzoCodec.java:180)
??????? at org.apache.hadoop.hive.ql.io.CodecPool.getDecompressor(CodecPool.java:122)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.init(RCFile.java:1117)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.<init>(RCFile.java:983)
??????? at org.apache.hadoop.hive.ql.io.RCFile$Reader.<init>(RCFile.java:964)
??????? at org.apache.hadoop.hive.ql.io.RCFileRecordReader.<init>(RCFileRecordReader.java:52)
??????? at org.apache.hadoop.hive.ql.io.RCFileInputFormat.getRecordReader(RCFileInputFormat.java:57)
??????? at org.apache.hadoop.hive.ql.exec.FetchOperator.getRecordReader(FetchOperator.java:306)
??????? at org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:320)
??????? ... 10 more

解决办法：在$hadoop_home/bin/hadoop文件中增加如下一行即可JAVA_LIBRARY_PATH=$hadoop_home/lib/native/Linux-amd64-64

在hadoop-0.20.205版本中处了该错误外，还有一个错误，就是找不到lzo的jar包，这是因为他们家在classpath的方法有了变更，默认不会把$hadoop_home/lib目录下的所有jar包都加载，所以在/conf/hadoop-env.sh中增加如下代码即可解决：export? HADOOP_CLASSPATH=$HADOOP_CLASSPATH:$hadoop_home/lib/hadoop-lzo.jar