org.apache.hadoop.mapreduce.lib.join

クラス OverrideRecordReader<K extends WritableComparable<?>,V extends Writable>

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<K,V>

org.apache.hadoop.mapreduce.lib.join.ComposableRecordReader<K,X>

org.apache.hadoop.mapreduce.lib.join.CompositeRecordReader<K,V,V>

org.apache.hadoop.mapreduce.lib.join.MultiFilterRecordReader<K,V>

org.apache.hadoop.mapreduce.lib.join.OverrideRecordReader<K,V>

すべての実装されたインタフェース:

Closeable, AutoCloseable, Comparable<ComposableRecordReader<K,?>>, Configurable

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class OverrideRecordReader<K extends WritableComparable<?>,V extends Writable>
extends MultiFilterRecordReader<K,V>

Prefer the "rightmost" data source for this key. For example, override(S1,S2,S3) will prefer values from S3 over S2, and values from S2 over S1 for all keys emitted from all sources.

フィールドのサマリー

クラスから継承されたフィールド org.apache.hadoop.mapreduce.lib.join.CompositeRecordReader

conf, jc, key, keyclass, kids, value

メソッドのサマリー

修飾子とタイプ	メソッドと説明
V	createValue() Create instance of value.
protected V	emit(TupleWritable dst) Emit the value with the highest position in the tuple.
protected void	fillJoinCollector(K iterkey) Instead of filling the JoinCollector with iterators from all data sources, fill only the rightmost for this key.

クラスから継承されたメソッド org.apache.hadoop.mapreduce.lib.join.MultiFilterRecordReader

combine, getDelegate, initialize, nextKeyValue

クラスから継承されたメソッド org.apache.hadoop.mapreduce.lib.join.CompositeRecordReader

accept, add, close, compareTo, createKey, createTupleWritable, getComparator, getConf, getCurrentKey, getCurrentValue, getProgress, getRecordReaderQueue, hasNext, id, key, key, setConf, skip

クラスから継承されたメソッド java.lang.Object

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

メソッドの詳細

emit

protected V emit(TupleWritable dst)

Emit the value with the highest position in the tuple.

定義:

emit クラス内 MultiFilterRecordReader<K extends WritableComparable<?>,V extends Writable>

createValue

public V createValue()

クラスからコピーされた説明: ComposableRecordReader

Create instance of value.

fillJoinCollector

protected void fillJoinCollector(K iterkey)
                          throws IOException,
                                 InterruptedException

Instead of filling the JoinCollector with iterators from all data sources, fill only the rightmost for this key. This not only saves space by discarding the other sources, but it also emits the number of key-value pairs in the preferred RecordReader instead of repeating that stream n times, where n is the cardinality of the cross product of the discarded streams for the given key.

オーバーライド:

fillJoinCollector クラス内 CompositeRecordReader<K extends WritableComparable<?>,V extends Writable,V extends Writable>

例外:

IOException

InterruptedException