## org.apache.hadoop.mapred.lib
Class NLineInputFormat

    java.lang.Object
      org.apache.hadoop.mapred.FileInputFormat<LongWritable,Text>
          org.apache.hadoop.mapred.lib.NLineInputFormat

All Implemented Interfaces:
  InputFormat<LongWritable,Text>, JobConfigurable

    public class NLineInputFormat

extends FileInputFormat<LongWritable,Text>
implements JobConfigurable

NLineInputFormat which splits N lines of input as one split. In many "pleasantly" parallel applications, each process/mapper processes the same input file (s), but with computations are controlled by different parameters.(Referred to as "parameter sweeps"). One way to achieve this, is to specify a set of parameters (one set per line) as input in a control file (which is the input path to the map-reduce application, where as the input dataset is specified via a config variable in JobConf.). The NLineInputFormat can be used in such applications, that splits the input file such that by default, one line is fed as a value to one map task, and key is the offset. i.e. (k,v) is (LongWritable, Text). The location hints will span the whole mapred cluster.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.mapred.FileInputFormat
`FileInputFormat.Counter`

Field Summary

Fields inherited from class org.apache.hadoop.mapred.FileInputFormat
`LOG`

Constructor Summary
`NLineInputFormat()`

Method Summary
`void` `configure(JobConf conf)` Initializes a new instance from a `JobConf`.
`RecordReader<LongWritable,Text>` `getRecordReader(InputSplit genericSplit, JobConf job, Reporter reporter)` Get the `RecordReader` for the given `InputSplit`.
`InputSplit[]` `getSplits(JobConf job, int numSplits)` Logically splits the set of input files for the job, splits N lines of the input as one split.

Methods inherited from class org.apache.hadoop.mapred.FileInputFormat
`addInputPath, addInputPaths, computeSplitSize, getBlockIndex, getInputPathFilter, getInputPaths, getSplitHosts, isSplitable, listStatus, setInputPathFilter, setInputPaths, setInputPaths, setMinSplitSize`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### NLineInputFormat

    public NLineInputFormat()

Method Detail

### getRecordReader

    public RecordReader<LongWritable,Text> getRecordReader(InputSplit genericSplit,
                                                           JobConf job,
                                                           Reporter reporter)
                                                    throws IOException

  Description copied from interface: `InputFormat`
  Get the `RecordReader` for the given `InputSplit`.

  It is the responsibility of the `RecordReader` to respect record boundaries while processing the logical split to present a record-oriented view to the individual task.

  Specified by:
    `getRecordReader` in interface `InputFormat<LongWritable,Text>`
  Specified by:
    `getRecordReader` in class `FileInputFormat<LongWritable,Text>`
  Parameters:
    `genericSplit` - the `InputSplit`
    `job` - the job that this split belongs to
  Returns:
    a `RecordReader`
  Throws:
    `IOException`

### getSplits

    public InputSplit[] getSplits(JobConf job,
                                  int numSplits)
                           throws IOException

  Logically splits the set of input files for the job, splits N lines of the input as one split.

  Specified by:
    `getSplits` in interface `InputFormat<LongWritable,Text>`
  Overrides:
    `getSplits` in class `FileInputFormat<LongWritable,Text>`
  Parameters:
    `job` - job configuration.
    `numSplits` - the desired number of splits, a hint.
  Returns:
    an array of `InputSplit`s for the job.
  Throws:
    `IOException`
  See Also:
    `FileInputFormat.getSplits(JobConf, int)`

### configure

    public void configure(JobConf conf)

  Description copied from interface: `JobConfigurable`
  Initializes a new instance from a `JobConf`.

  Specified by:
    `configure` in interface `JobConfigurable`
  Parameters:
    `conf` - the configuration

Copyright © 2009 The Apache Software Foundation