org.apache.hadoop.mapred.join
Class MultiFilterRecordReader<K extends WritableComparable,V extends Writable>

java.lang.Object
  org.apache.hadoop.mapred.join.CompositeRecordReader<K,V,V>
      org.apache.hadoop.mapred.join.MultiFilterRecordReader<K,V>

All Implemented Interfaces:

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

Direct Known Subclasses:

OverrideRecordReader

public abstract class MultiFilterRecordReader<K extends WritableComparable,V extends Writable>
extends CompositeRecordReader<K,V,V>
implements ComposableRecordReader<K,V>

Base class for Composite join returning values derived from multiple sources, but generally not tuples.

Nested Class Summary

protected class

MultiFilterRecordReader.MultiFilterDelegationIterator Proxy the JoinCollector, but include callback to emit.

Field Summary

Fields inherited from class org.apache.hadoop.mapred.join.CompositeRecordReader

jc, kids

Constructor Summary

MultiFilterRecordReader(int id, JobConf conf, int capacity, Class<? extends WritableComparator> cmpcl)

Method Summary

protected boolean	combine(Object[] srcs, TupleWritable dst) Default implementation offers emit(org.apache.hadoop.mapred.join.TupleWritable) every Tuple from the collector (the outer join of child RRs).
V	createValue() Create an object of the appropriate type to be used as a value.
protected abstract V	emit(TupleWritable dst) For each tuple emitted, return a value (typically one of the values in the tuple).
protected ResetableIterator<V>	getDelegate() Return an iterator returning a single value from the tuple.
boolean	next(K key, V value) Reads the next key/value pair from the input for processing.

Methods inherited from class org.apache.hadoop.mapred.join.CompositeRecordReader

accept, add, close, compareTo, createInternalValue, createKey, fillJoinCollector, getComparator, getConf, getPos, getProgress, getRecordReaderQueue, hasNext, id, key, key, setConf, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.hadoop.mapred.join.ComposableRecordReader

accept, hasNext, id, key, key, skip

Methods inherited from interface org.apache.hadoop.mapred.RecordReader

close, createKey, getPos, getProgress

Methods inherited from interface java.lang.Comparable

compareTo

Constructor Detail

MultiFilterRecordReader

public MultiFilterRecordReader(int id,
                               JobConf conf,
                               int capacity,
                               Class<? extends WritableComparator> cmpcl)
                        throws IOException

Throws:

IOException

Method Detail

emit

protected abstract V emit(TupleWritable dst)
                                    throws IOException

For each tuple emitted, return a value (typically one of the values in the tuple). Modifying the Writables in the tuple is permitted and unlikely to affect join behavior in most cases, but it is not recommended. It's safer to clone first.

Throws:

IOException

combine

protected boolean combine(Object[] srcs,
                          TupleWritable dst)

Default implementation offers emit(org.apache.hadoop.mapred.join.TupleWritable) every Tuple from the collector (the outer join of child RRs).

Specified by:

combine in class CompositeRecordReader<K extends WritableComparable,V extends Writable,V extends Writable>

next

public boolean next(K key,
                    V value)
             throws IOException

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

Specified by:

next in interface RecordReader<K extends WritableComparable,V 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

createValue

public V createValue()

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

Specified by:

createValue in interface RecordReader<K extends WritableComparable,V extends Writable>

Returns:

a new value object.

getDelegate

protected ResetableIterator<V> getDelegate()

Return an iterator returning a single value from the tuple.

Specified by:

getDelegate in class CompositeRecordReader<K extends WritableComparable,V extends Writable,V extends Writable>

See Also:

MultiFilterRecordReader.MultiFilterDelegationIterator