org.apache.hadoop.mapred.join

类 OverrideRecordReader<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>

org.apache.hadoop.mapred.join.OverrideRecordReader<K,V>

所有已实现的接口:

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

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.

嵌套类概要

从类继承的嵌套类/接口 org.apache.hadoop.mapred.join.MultiFilterRecordReader

MultiFilterRecordReader.MultiFilterDelegationIterator

字段概要

从类继承的字段 org.apache.hadoop.mapred.join.CompositeRecordReader

jc, kids

方法概要

方法

限定符和类型	方法和说明
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.

从类继承的方法 org.apache.hadoop.mapred.join.MultiFilterRecordReader

combine, createValue, getDelegate, next

从类继承的方法 org.apache.hadoop.mapred.join.CompositeRecordReader

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

从类继承的方法 java.lang.Object

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

从接口继承的方法 org.apache.hadoop.mapred.join.ComposableRecordReader

accept, hasNext, id, key, key, skip

从接口继承的方法 org.apache.hadoop.mapred.RecordReader

close, createKey, getPos, getProgress

从接口继承的方法 java.lang.Comparable

compareTo

方法详细资料

emit

protected V emit(TupleWritable dst)

Emit the value with the highest position in the tuple.

指定者:

emit 在类中 MultiFilterRecordReader<K extends WritableComparable,V extends Writable>

fillJoinCollector

protected void fillJoinCollector(K iterkey)
                          throws IOException

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.

覆盖:

fillJoinCollector 在类中 CompositeRecordReader<K extends WritableComparable,V extends Writable,V extends Writable>

抛出:

IOException