org.apache.hadoop.mapred.join
Class WrappedRecordReader<K extends WritableComparable,U extends Writable>

java.lang.Object
  extended by org.apache.hadoop.mapred.join.WrappedRecordReader<K,U>
All Implemented Interfaces:
Comparable<ComposableRecordReader<K,?>>, ComposableRecordReader<K,U>, RecordReader<K,U>

@InterfaceAudience.Public
@InterfaceStability.Stable
public class WrappedRecordReader<K extends WritableComparable,U extends Writable>
extends Object
implements ComposableRecordReader<K,U>

Proxy class for a RecordReader participating in the join framework. This class keeps track of the "head" key-value pair for the provided RecordReader and keeps a store of values matching a key when this source is participating in a join.


Method Summary
 void accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector i, K key)
          Add an iterator to the collector at the position occupied by this RecordReader over the values in this stream paired with the key provided (ie register a stream of values from this source matching K with a collector).
 void close()
          Forward close request to proxied RR.
 int compareTo(ComposableRecordReader<K,?> other)
          Implement Comparable contract (compare key at head of proxied RR with that of another).
 K createKey()
          Request new key from proxied RR.
 U createValue()
          Request new value from proxied RR.
 boolean equals(Object other)
          Return true iff compareTo(other) retn true.
 long getPos()
          Request position from proxied RR.
 float getProgress()
          Request progress from proxied RR.
 int hashCode()
           
 boolean hasNext()
          Return true if the RR- including the k,v pair stored in this object- is exhausted.
 int id()
          Return the position in the collector this class occupies.
 K key()
          Return the key at the head of this RR.
 void key(K qkey)
          Clone the key at the head of this RR into the object supplied.
protected  boolean next()
          Read the next k,v pair into the head of this object; return true iff the RR and this are exhausted.
 boolean next(K key, U value)
          Write key-value pair at the head of this stream to the objects provided; get next key-value pair from proxied RR.
 void skip(K key)
          Skip key-value pairs with keys less than or equal to the key provided.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

id

public int id()
Return the position in the collector this class occupies.

Specified by:
id in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>

key

public K key()
Return the key at the head of this RR.

Specified by:
key in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>

key

public void key(K qkey)
         throws IOException
Clone the key at the head of this RR into the object supplied.

Specified by:
key in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>
Throws:
IOException

hasNext

public boolean hasNext()
Return true if the RR- including the k,v pair stored in this object- is exhausted.

Specified by:
hasNext in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>

skip

public void skip(K key)
          throws IOException
Skip key-value pairs with keys less than or equal to the key provided.

Specified by:
skip in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>
Throws:
IOException

next

protected boolean next()
                throws IOException
Read the next k,v pair into the head of this object; return true iff the RR and this are exhausted.

Throws:
IOException

accept

public void accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector i,
                   K key)
            throws IOException
Add an iterator to the collector at the position occupied by this RecordReader over the values in this stream paired with the key provided (ie register a stream of values from this source matching K with a collector).

Specified by:
accept in interface ComposableRecordReader<K extends WritableComparable,U extends Writable>
Throws:
IOException

next

public boolean next(K key,
                    U value)
             throws IOException
Write key-value pair at the head of this stream to the objects provided; get next key-value pair from proxied RR.

Specified by:
next in interface RecordReader<K extends WritableComparable,U extends Writable>
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

public K createKey()
Request new key from proxied RR.

Specified by:
createKey in interface RecordReader<K extends WritableComparable,U extends Writable>
Returns:
a new key object.

createValue

public U createValue()
Request new value from proxied RR.

Specified by:
createValue in interface RecordReader<K extends WritableComparable,U extends Writable>
Returns:
a new value object.

getProgress

public float getProgress()
                  throws IOException
Request progress from proxied RR.

Specified by:
getProgress in interface RecordReader<K extends WritableComparable,U extends Writable>
Returns:
progress from 0.0 to 1.0.
Throws:
IOException

getPos

public long getPos()
            throws IOException
Request position from proxied RR.

Specified by:
getPos in interface RecordReader<K extends WritableComparable,U extends Writable>
Returns:
the current position in the input.
Throws:
IOException

close

public void close()
           throws IOException
Forward close request to proxied RR.

Specified by:
close in interface RecordReader<K extends WritableComparable,U extends Writable>
Throws:
IOException

compareTo

public int compareTo(ComposableRecordReader<K,?> other)
Implement Comparable contract (compare key at head of proxied RR with that of another).

Specified by:
compareTo in interface Comparable<ComposableRecordReader<K extends WritableComparable,?>>

equals

public boolean equals(Object other)
Return true iff compareTo(other) retn true.

Overrides:
equals in class Object

hashCode

public int hashCode()
Overrides:
hashCode in class Object


Copyright © 2012 Apache Software Foundation. All Rights Reserved.