| Package | Description | 
|---|---|
| org.apache.hadoop.io | Generic i/o code for use when reading and writing data to the network,
to databases, and to files. | 
| org.apache.hadoop.mapred | |
| org.apache.hadoop.mapred.join | |
| org.apache.hadoop.mapred.lib.aggregate | |
| org.apache.hadoop.mapreduce | |
| org.apache.hadoop.mapreduce.lib.aggregate | |
| org.apache.hadoop.mapreduce.lib.join | |
| org.apache.hadoop.mapreduce.lib.output | |
| org.apache.hadoop.record | 
    (DEPRECATED) Hadoop record I/O contains classes and a record description language
    translator for simplifying serialization and deserialization of records in a
    language-neutral manner. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | SortedMapWritable<K extends WritableComparable<? super K>>A Writable SortedMap. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | BooleanWritableA WritableComparable for booleans. | 
| class  | BytesWritableA byte sequence that is usable as a key or value. | 
| class  | ByteWritableA WritableComparable for a single byte. | 
| class  | DoubleWritableWritable for Double values. | 
| class  | FloatWritableA WritableComparable for floats. | 
| class  | IntWritableA WritableComparable for ints. | 
| class  | LongWritableA WritableComparable for longs. | 
| class  | MD5HashA Writable for MD5 hash values. | 
| class  | NullWritableSingleton Writable with no data. | 
| class  | ShortWritableA WritableComparable for shorts. | 
| class  | TextThis class stores text using standard UTF8 encoding. | 
| class  | VIntWritableA WritableComparable for integer values stored in variable-length format. | 
| class  | VLongWritableA WritableComparable for longs in a variable-length format. | 
| Modifier and Type | Method and Description | 
|---|---|
| WritableComparable | WritableComparator. newKey()Construct a new  WritableComparableinstance. | 
| Modifier and Type | Method and Description | 
|---|---|
| Class<? extends WritableComparable> | WritableComparator. getKeyClass()Returns the WritableComparable implementation class. | 
| Modifier and Type | Method and Description | 
|---|---|
| int | WritableComparator. compare(WritableComparable a,
       WritableComparable b)Compare two WritableComparables. | 
| int | WritableComparator. compare(WritableComparable a,
       WritableComparable b)Compare two WritableComparables. | 
| Modifier and Type | Method and Description | 
|---|---|
| static WritableComparator | WritableComparator. get(Class<? extends WritableComparable> c)For backwards compatibility. | 
| static WritableComparator | WritableComparator. get(Class<? extends WritableComparable> c,
   Configuration conf)Get a comparator for a  WritableComparableimplementation. | 
| Constructor and Description | 
|---|
| WritableComparator(Class<? extends WritableComparable> keyClass)Construct for a  WritableComparableimplementation. | 
| WritableComparator(Class<? extends WritableComparable> keyClass,
                  boolean createInstances) | 
| WritableComparator(Class<? extends WritableComparable> keyClass,
                  Configuration conf,
                  boolean createInstances) | 
| Modifier and Type | Method and Description | 
|---|---|
| static <K extends WritableComparable,V extends Writable> | MapFileOutputFormat. getEntry(org.apache.hadoop.io.MapFile.Reader[] readers,
        Partitioner<K,V> partitioner,
        K key,
        V value)Get an entry from output generated by this class. | 
| Modifier and Type | Method and Description | 
|---|---|
| RecordWriter<WritableComparable,Writable> | MapFileOutputFormat. getRecordWriter(FileSystem ignored,
               JobConf job,
               String name,
               Progressable progress) | 
| static Class<? extends WritableComparable> | SequenceFileAsBinaryOutputFormat. getSequenceFileOutputKeyClass(JobConf conf)Get the key class for the  SequenceFile | 
| Modifier and Type | Interface and Description | 
|---|---|
| interface  | ComposableInputFormat<K extends WritableComparable,V extends Writable>Refinement of InputFormat requiring implementors to provide
 ComposableRecordReader instead of RecordReader. | 
| interface  | ComposableRecordReader<K extends WritableComparable,V extends Writable>Additional operations required of a RecordReader to participate in a join. | 
| class  | CompositeInputFormat<K extends WritableComparable>An InputFormat capable of performing joins over a set of data sources sorted
 and partitioned the same way. | 
| class  | CompositeRecordReader<K extends WritableComparable,V extends Writable,X extends Writable>A RecordReader that can effect joins of RecordReaders sharing a common key
 type and partitioning. | 
| class  | InnerJoinRecordReader<K extends WritableComparable>Full inner join. | 
| class  | JoinRecordReader<K extends WritableComparable>Base class for Composite joins returning Tuples of arbitrary Writables. | 
| class  | MultiFilterRecordReader<K extends WritableComparable,V extends Writable>Base class for Composite join returning values derived from multiple
 sources, but generally not tuples. | 
| class  | OuterJoinRecordReader<K extends WritableComparable>Full outer join. | 
| class  | OverrideRecordReader<K extends WritableComparable,V extends Writable>Prefer the "rightmost" data source for this key. | 
| class  | WrappedRecordReader<K extends WritableComparable,U extends Writable>Proxy class for a RecordReader participating in the join framework. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | ValueAggregatorCombiner<K1 extends WritableComparable,V1 extends Writable>This class implements the generic combiner of Aggregate. | 
| class  | ValueAggregatorJobBase<K1 extends WritableComparable,V1 extends Writable>This abstract class implements some common functionalities of the
 the generic mapper, reducer and combiner classes of Aggregate. | 
| class  | ValueAggregatorMapper<K1 extends WritableComparable,V1 extends Writable>This class implements the generic mapper of Aggregate. | 
| class  | ValueAggregatorReducer<K1 extends WritableComparable,V1 extends Writable>This class implements the generic reducer of Aggregate. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | IDA general identifier, which internally stores the id
 as an integer. | 
| class  | JobIDJobID represents the immutable and unique identifier for 
 the job. | 
| class  | TaskAttemptIDTaskAttemptID represents the immutable and unique identifier for 
 a task attempt. | 
| class  | TaskIDTaskID represents the immutable and unique identifier for 
 a Map or Reduce Task. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | ValueAggregatorCombiner<K1 extends WritableComparable<?>,V1 extends Writable>This class implements the generic combiner of Aggregate. | 
| class  | ValueAggregatorJobBase<K1 extends WritableComparable<?>,V1 extends Writable>This abstract class implements some common functionalities of the
 the generic mapper, reducer and combiner classes of Aggregate. | 
| class  | ValueAggregatorMapper<K1 extends WritableComparable<?>,V1 extends Writable>This class implements the generic mapper of Aggregate. | 
| class  | ValueAggregatorReducer<K1 extends WritableComparable<?>,V1 extends Writable>This class implements the generic reducer of Aggregate. | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | ComposableInputFormat<K extends WritableComparable<?>,V extends Writable>Refinement of InputFormat requiring implementors to provide
 ComposableRecordReader instead of RecordReader. | 
| class  | ComposableRecordReader<K extends WritableComparable<?>,V extends Writable>Additional operations required of a RecordReader to participate in a join. | 
| class  | CompositeInputFormat<K extends WritableComparable>An InputFormat capable of performing joins over a set of data sources sorted
 and partitioned the same way. | 
| class  | CompositeRecordReader<K extends WritableComparable<?>,V extends Writable,X extends Writable>A RecordReader that can effect joins of RecordReaders sharing a common key
 type and partitioning. | 
| class  | InnerJoinRecordReader<K extends WritableComparable<?>>Full inner join. | 
| class  | JoinRecordReader<K extends WritableComparable<?>>Base class for Composite joins returning Tuples of arbitrary Writables. | 
| class  | MultiFilterRecordReader<K extends WritableComparable<?>,V extends Writable>Base class for Composite join returning values derived from multiple
 sources, but generally not tuples. | 
| class  | OuterJoinRecordReader<K extends WritableComparable<?>>Full outer join. | 
| class  | OverrideRecordReader<K extends WritableComparable<?>,V extends Writable>Prefer the "rightmost" data source for this key. | 
| class  | WrappedRecordReader<K extends WritableComparable<?>,U extends Writable>Proxy class for a RecordReader participating in the join framework. | 
| Modifier and Type | Field and Description | 
|---|---|
| protected K | CompositeRecordReader. key | 
| Modifier and Type | Field and Description | 
|---|---|
| protected Class<? extends WritableComparable> | CompositeRecordReader. keyclass | 
| Modifier and Type | Method and Description | 
|---|---|
| static <K extends WritableComparable<?>,V extends Writable> | MapFileOutputFormat. getEntry(org.apache.hadoop.io.MapFile.Reader[] readers,
        Partitioner<K,V> partitioner,
        K key,
        V value)Get an entry from output generated by this class. | 
| Modifier and Type | Method and Description | 
|---|---|
| RecordWriter<WritableComparable<?>,Writable> | MapFileOutputFormat. getRecordWriter(TaskAttemptContext context) | 
| static Class<? extends WritableComparable> | SequenceFileAsBinaryOutputFormat. getSequenceFileOutputKeyClass(JobContext job)Get the key class for the  SequenceFile | 
| Modifier and Type | Class and Description | 
|---|---|
| class  | RecordDeprecated. 
 Replaced by Avro. | 
| Constructor and Description | 
|---|
| RecordComparator(Class<? extends WritableComparable> recordClass)Deprecated.  Construct a raw  Recordcomparison implementation. | 
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