ComposableRecordReader (Hadoop 1.2.1 API)
Date: 2013-07-22

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## org.apache.hadoop.mapred.join
Interface ComposableRecordReader<K extends WritableComparable,V extends Writable>

All Superinterfaces:
  Comparable<ComposableRecordReader<K,?>>, RecordReader<K,V>

All Known Implementing Classes:
  InnerJoinRecordReader, JoinRecordReader, MultiFilterRecordReader, OuterJoinRecordReader, OverrideRecordReader, WrappedRecordReader

    public interface ComposableRecordReader<K extends WritableComparable,V extends Writable>

extends RecordReader<K,V>, Comparable<ComposableRecordReader<K,?>>

Additional operations required of a RecordReader to participate in a join.

Method Summary
`void` | `accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc, K key)` While key-value pairs from this RecordReader match the given key, register them with the JoinCollector provided.
`boolean` | `hasNext()` Returns true if the stream is not empty, but provides no guarantee that a call to next(K,V) will succeed.
`int` | `id()` Return the position in the collector this class occupies.
`K` | `key()` Return the key this RecordReader would supply on a call to next(K,V)
`void` | `key(K key)` Clone the key at the head of this RecordReader into the object provided.
`void` | `skip(K key)` Skip key-value pairs with keys less than or equal to the key provided.

Methods inherited from interface org.apache.hadoop.mapred.RecordReader
`close, createKey, createValue, getPos, getProgress, next`

Methods inherited from interface java.lang.Comparable
`compareTo`

Method Detail

### id

    int id()

  Return the position in the collector this class occupies.

### key

    K key()

  Return the key this RecordReader would supply on a call to next(K,V)

### key

    void key(K key)
             throws IOException

  Clone the key at the head of this RecordReader into the object provided.

  Throws:
    `IOException`

### hasNext

    boolean hasNext()

  Returns true if the stream is not empty, but provides no guarantee that a call to next(K,V) will succeed.

### skip

    void skip(K key)
              throws IOException

  Skip key-value pairs with keys less than or equal to the key provided.

  Throws:
    `IOException`

### accept

    void accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc,
                K key)
                throws IOException

  While key-value pairs from this RecordReader match the given key, register them with the JoinCollector provided.

  Throws:
    `IOException`

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