cascading.scheme
Class WritableSequenceFile

java.lang.Object
  cascading.scheme.Scheme
      cascading.scheme.SequenceFile
          cascading.scheme.WritableSequenceFile

All Implemented Interfaces:

Serializable

public class WritableSequenceFile
extends SequenceFile

Class WritableSequenceFile is a sub-class of SequenceFile that reads and writes values of the given writableType Class, instead of Tuple instances used by default in SequenceFile.

This Class is a convenience for those who need to read/write specific types from existing sequence files without them being wrapped in a Tuple instance.

Note due to the nature of sequence files, only one type can be stored in the key and value positions, they they can be uniquely different types (LongWritable, Text).

If keyType is null, valueType must not be null, and vice versa, assuming you only wish to store a single value.

NullWritable is used as the empty type for either a null keyType or valueType.

See Also:

Serialized Form

Field Summary

protected Class<? extends Writable>	keyType
protected Class<? extends Writable>	valueType

Constructor Summary

WritableSequenceFile(Fields fields, Class<? extends Writable> valueType)
Constructor WritableSequenceFile creates a new WritableSequenceFile instance.

WritableSequenceFile(Fields fields, Class<? extends Writable> keyType, Class<? extends Writable> valueType)
Constructor WritableSequenceFile creates a new WritableSequenceFile instance.

Method Summary

boolean	equals(Object object)
int	hashCode()
void	sink(TupleEntry tupleEntry, OutputCollector outputCollector) Method sink writes out the given Tuple instance to the outputCollector.
void	sinkInit(Tap tap, JobConf conf) Method sinkInit initializes this instance as a sink.
Tuple	source(Object key, Object value) Method source takes the given Hadoop key and value and returns a new Tuple instance.

Methods inherited from class cascading.scheme.SequenceFile

sourceInit

Methods inherited from class cascading.scheme.Scheme

getNumSinkParts, getSinkFields, getSourceFields, getTrace, isSink, isSource, isSymmetrical, isWriteDirect, setNumSinkParts, setSinkFields, setSourceFields, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

keyType

protected Class<? extends Writable> keyType

valueType

protected Class<? extends Writable> valueType

Constructor Detail

WritableSequenceFile

@ConstructorProperties(value={"fields","valueType"})
public WritableSequenceFile(Fields fields,
                                                       Class<? extends Writable> valueType)

Constructor WritableSequenceFile creates a new WritableSequenceFile instance.

Parameters:

fields - of type Fields

valueType - of type Class, may not be null

WritableSequenceFile

@ConstructorProperties(value={"fields","keyType","valueType"})
public WritableSequenceFile(Fields fields,
                                                       Class<? extends Writable> keyType,
                                                       Class<? extends Writable> valueType)

Constructor WritableSequenceFile creates a new WritableSequenceFile instance.

Parameters:

fields - of type Fields

keyType - of type Class

valueType - of type Class

Method Detail

sinkInit

public void sinkInit(Tap tap,
                     JobConf conf)

Description copied from class: Scheme

Method sinkInit initializes this instance as a sink.

Overrides:

sinkInit in class SequenceFile

Parameters:

tap - of type Tap

conf - of type JobConf

source

public Tuple source(Object key,
                    Object value)

Description copied from class: Scheme

Method source takes the given Hadoop key and value and returns a new Tuple instance.

Overrides:

source in class SequenceFile

Parameters:

key - of type WritableComparable

value - of type Writable

Returns:

Tuple

sink

public void sink(TupleEntry tupleEntry,
                 OutputCollector outputCollector)
          throws IOException

Description copied from class: Scheme

Method sink writes out the given Tuple instance to the outputCollector.

Overrides:

sink in class SequenceFile

outputCollector - of type OutputCollector @throws IOException when

Throws:

IOException

equals

public boolean equals(Object object)

Overrides:

equals in class Scheme

hashCode

public int hashCode()

Overrides:

hashCode in class Scheme