RecordReader (Hadoop 0.20.2+737 API)
Date: 2010-10-11

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## org.apache.hadoop.mapred
Interface RecordReader<K,V>

All Known Subinterfaces:
  ComposableRecordReader<K,V>

All Known Implementing Classes:
  CombineFileRecordReader, DBInputFormat.DBRecordReader, InnerJoinRecordReader, JoinRecordReader, KeyValueLineRecordReader, LineDocRecordReader, LineRecordReader, MultiFilterRecordReader, OuterJoinRecordReader, OverrideRecordReader, SequenceFileAsBinaryInputFormat.SequenceFileAsBinaryRecordReader, SequenceFileAsTextRecordReader, SequenceFileRecordReader, StreamBaseRecordReader, StreamXmlRecordReader, WrappedRecordReader

    public interface RecordReader<K,V>

`RecordReader` reads <key, value> pairs from an `InputSplit`.

`RecordReader`, typically, converts the byte-oriented view of the input, provided by the `InputSplit`, and presents a record-oriented view for the `Mapper` & `Reducer` tasks for processing. It thus assumes the responsibility of processing record boundaries and presenting the tasks with keys and values.

See Also:
  `InputSplit`, `InputFormat`

Method Summary
`void` | `close()` Close this `InputSplit` to future operations.
`K` | `createKey()` Create an object of the appropriate type to be used as a key.
`V` | `createValue()` Create an object of the appropriate type to be used as a value.
`long` | `getPos()` Returns the current position in the input.
`float` | `getProgress()` How much of the input has the `RecordReader` consumed i.e.
`boolean` | `next(K key, V value)` Reads the next key/value pair from the input for processing.

Method Detail

### next

    boolean next(K key,
                 V value)
                 throws IOException

  Reads the next key/value pair from the input for processing.

  Parameters:
    `key` - the key to read data into
    `value` - the value to read data into
  Returns:
    true iff a key/value was read, false if at EOF
  Throws:
    `IOException`

### createKey

    K createKey()

  Create an object of the appropriate type to be used as a key.

  Returns:
    a new key object.

### createValue

    V createValue()

  Create an object of the appropriate type to be used as a value.

  Returns:
    a new value object.

### getPos

    long getPos()
                throws IOException

  Returns the current position in the input.

  Returns:
    the current position in the input.
  Throws:
    `IOException`

### close

    void close()
               throws IOException

  Close this `InputSplit` to future operations.

  Throws:
    `IOException`

### getProgress

    float getProgress()
                      throws IOException

  How much of the input has the `RecordReader` consumed i.e. has been processed by?

  Returns:
    progress from `0.0` to `1.0`.
  Throws:
    `IOException`

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