Accessing Table Data with MapReduce

You can download an example of a MapReduce program that reads from the groups table (consisting of data from /etc/group), extracts the first and third columns, and inserts them into the groupids table. Proceed as follows.
  1. Download the program from https://github.com/cloudera/hcatalog-examples.git.
  2. Build the example JAR file: 
    $ cd hcatalog-examples 
$ mvn package
  3. Load data from the local filesystem into the groups table: 
    $ hive -e "load data local inpath '/etc/group' overwrite into table groups"
  4. Set up the environment that is needed for copying the required JAR files to HDFS, for example: 
    $ export HCAT_HOME=/usr/lib/hive-hcatalog
$ export HIVE_HOME=/usr/lib/hive
$ HIVE_VERSION=0.11.0-cdh5.0.0
$ HCATJAR=$HCAT_HOME/share/hcatalog/hcatalog-core-$HIVE_VERSION.jar
$ HCATPIGJAR=$HCAT_HOME/share/hcatalog/hcatalog-pig-adapter-$HIVE_VERSION.jar
$ export HADOOP_CLASSPATH=$HCATJAR:$HCATPIGJAR:$HIVE_HOME/lib/hive-exec-$HIVE_VERSION.jar\
:$HIVE_HOME/lib/hive-metastore-$HIVE_VERSION.jar:$HIVE_HOME/lib/jdo-api-*.jar:$HIVE_HOME/lib/libfb303-*.jar\
:$HIVE_HOME/lib/libthrift-*.jar:$HIVE_HOME/lib/slf4j-api-*.jar:$HIVE_HOME/conf:/etc/hadoop/conf
$ LIBJARS=`echo $HADOOP_CLASSPATH | sed -e 's/:/,/g'`
$ export LIBJARS=$LIBJARS,$HIVE_HOME/lib/antlr-runtime-*.jar
  5. Run the job: 
    $ hadoop jar target/UseHCat-1.0.jar com.cloudera.test.UseHCat -files $HCATJAR -libjars $LIBJARS groups groupids