Field Detail

• GROUP_COLUMNS

  public static final String GROUP_COLUMNS

  JobConf parameter to specify the columns used to produce the key passed to collect from the map phase.

  See Also:

  Constant Field Values

• columns

  protected byte[][] columns

  The grouping columns.

Constructor Detail

• GroupingTableMapper

  public GroupingTableMapper()

Method Detail

• initJob

  public static void initJob(String table,
             Scan scan,
             String groupColumns,
             Class<? extends TableMapper> mapper,
             org.apache.hadoop.mapreduce.Job job)
                      throws IOException

  Use this before submitting a TableMap job. It will appropriately set up the job.

  Parameters:

  table - The table to be processed.

  scan - The scan with the columns etc.

  groupColumns - A space separated list of columns used to form the key used in collect.

  mapper - The mapper class.

  job - The current job.

  Throws:

  IOException - When setting up the job fails.

• map

  public void map(ImmutableBytesWritable key,
         Result value,
         org.apache.hadoop.mapreduce.Mapper.Context context)
           throws IOException,
                  InterruptedException

  Extract the grouping columns from value to construct a new key. Pass the new key and value to reduce. If any of the grouping columns are not found in the value, the record is skipped.

  Overrides:

  map in class org.apache.hadoop.mapreduce.Mapper<ImmutableBytesWritable,Result,ImmutableBytesWritable,Result>

  Parameters:

  key - The current key.

  value - The current value.

  context - The current context.

  Throws:

  IOException - When writing the record fails.

  InterruptedException - When the job is aborted.

• extractKeyValues

  protected byte[][] extractKeyValues(Result r)

  Extract columns values from the current record. This method returns null if any of the columns are not found.

  Override this method if you want to deal with nulls differently.

  Parameters:

  r - The current values.

  Returns:

  Array of byte values.

• createGroupKey

  protected ImmutableBytesWritable createGroupKey(byte[][] vals)

  Create a key by concatenating multiple column values.

  Override this function in order to produce different types of keys.

  Parameters:

  vals - The current key/values.

  Returns:

  A key generated by concatenating multiple column values.

• getConf

  public org.apache.hadoop.conf.Configuration getConf()

  Returns the current configuration.

  Specified by:

  getConf in interface org.apache.hadoop.conf.Configurable

  Returns:

  The current configuration.

  See Also:

  Configurable.getConf()

• setConf

  public void setConf(org.apache.hadoop.conf.Configuration configuration)

  Sets the configuration. This is used to set up the grouping details.

  Specified by:

  setConf in interface org.apache.hadoop.conf.Configurable

  Parameters:

  configuration - The configuration to set.

  See Also:

  Configurable.setConf( org.apache.hadoop.conf.Configuration)