cascading.tap.local
Class PartitionTap
java.lang.Object
cascading.tap.Tap<Config,Input,Output>
cascading.tap.partition.BasePartitionTap<Properties,InputStream,OutputStream>
cascading.tap.local.PartitionTap
- All Implemented Interfaces:
- FlowElement, Traceable, Serializable
public class PartitionTap
- extends BasePartitionTap<Properties,InputStream,OutputStream>
Class PartitionTap can be used to write tuple streams out to files and sub-directories based on the values in the
current Tuple
instance.
The constructor takes a FileTap
Tap
and a Partition
implementation. This allows Tuple values at given positions to be used as directory names during write
operations, and directory names as data during read operations.
The key value here is that there is no need to duplicate data values in the directory names and inside
the data files.
So only values declared in the parent Tap will be read or written to the underlying file system files. But
fields declared by the Partition
will only be read or written to the directory names. That is, the
PartitionTap instance will sink or source the partition fields, plus the parent Tap fields. The partition
fields and parent Tap fields do not need to have common field names.
openWritesThreshold
limits the number of open files to be output to. This value defaults to 300 files.
Each time the threshold is exceeded, 10% of the least recently used open files will be closed.
PartitionTap will populate a given partition
without regard to case of the values being used. Thus
the resulting paths 2012/June/
and 2012/june/
will likely result in two open files into the same
location. Forcing the case to be consistent with a custom Partition implementation or an upstream
Function
is recommended, see ExpressionFunction
.
- See Also:
- Serialized Form
Constructor Summary |
PartitionTap(FileTap parent,
Partition partition)
Constructor PartitionTap creates a new PartitionTap instance using the given parent FileTap Tap as the
base path and default Scheme , and the partition. |
PartitionTap(FileTap parent,
Partition partition,
int openWritesThreshold)
Constructor PartitionTap creates a new PartitionTap instance using the given parent FileTap Tap as the
base path and default Scheme , and the partition. |
PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode)
Constructor PartitionTap creates a new PartitionTap instance using the given parent FileTap Tap as the
base path and default Scheme , and the partition. |
PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode,
boolean keepParentOnDelete)
Constructor PartitionTap creates a new PartitionTap instance using the given parent FileTap Tap as the
base path and default Scheme , and the partition. |
PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode,
boolean keepParentOnDelete,
int openWritesThreshold)
Constructor PartitionTap creates a new PartitionTap instance using the given parent FileTap Tap as the
base path and default Scheme , and the partition. |
Methods inherited from class cascading.tap.partition.BasePartitionTap |
commitResource, createResource, equals, getChildPartitionIdentifiers, getIdentifier, getModifiedTime, getOpenWritesThreshold, getParent, getPartition, hashCode, openForRead, openForWrite, resourceExists, rollbackResource, toString |
Methods inherited from class cascading.tap.Tap |
createResource, deleteResource, flowConfInit, getConfigDef, getFullIdentifier, getFullIdentifier, getModifiedTime, getScheme, getSinkFields, getSinkMode, getSourceFields, getStepConfigDef, getTrace, hasConfigDef, hasStepConfigDef, id, isEquivalentTo, isKeep, isReplace, isSink, isSource, isTemporary, isUpdate, openForRead, openForWrite, outgoingScopeFor, presentSinkFields, presentSourceFields, resolveIncomingOperationArgumentFields, resolveIncomingOperationPassThroughFields, resourceExists, retrieveSinkFields, retrieveSourceFields, setScheme, sinkConfInit, sourceConfInit, taps |
PartitionTap
@ConstructorProperties(value={"parent","partition"})
public PartitionTap(FileTap parent,
Partition partition)
- Constructor PartitionTap creates a new PartitionTap instance using the given parent
FileTap
Tap as the
base path and default Scheme
, and the partition.
- Parameters:
parent
- of type Tappartition
- of type String
PartitionTap
@ConstructorProperties(value={"parent","partition","openWritesThreshold"})
public PartitionTap(FileTap parent,
Partition partition,
int openWritesThreshold)
- Constructor PartitionTap creates a new PartitionTap instance using the given parent
FileTap
Tap as the
base path and default Scheme
, and the partition.
openWritesThreshold
limits the number of open files to be output to.
- Parameters:
parent
- of type Hfspartition
- of type StringopenWritesThreshold
- of type int
PartitionTap
@ConstructorProperties(value={"parent","partition","sinkMode"})
public PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode)
- Constructor PartitionTap creates a new PartitionTap instance using the given parent
FileTap
Tap as the
base path and default Scheme
, and the partition.
- Parameters:
parent
- of type Tappartition
- of type StringsinkMode
- of type SinkMode
PartitionTap
@ConstructorProperties(value={"parent","partition","sinkMode","keepParentOnDelete"})
public PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode,
boolean keepParentOnDelete)
- Constructor PartitionTap creates a new PartitionTap instance using the given parent
FileTap
Tap as the
base path and default Scheme
, and the partition.
keepParentOnDelete
, when set to true, prevents the parent Tap from being deleted when BasePartitionTap.deleteResource(Object)
is called, typically an issue when used inside a Cascade
.
- Parameters:
parent
- of type Tappartition
- of type StringsinkMode
- of type SinkModekeepParentOnDelete
- of type boolean
PartitionTap
@ConstructorProperties(value={"parent","partition","sinkMode","keepParentOnDelete","openWritesThreshold"})
public PartitionTap(FileTap parent,
Partition partition,
SinkMode sinkMode,
boolean keepParentOnDelete,
int openWritesThreshold)
- Constructor PartitionTap creates a new PartitionTap instance using the given parent
FileTap
Tap as the
base path and default Scheme
, and the partition.
keepParentOnDelete
, when set to true, prevents the parent Tap from being deleted when BasePartitionTap.deleteResource(Object)
is called, typically an issue when used inside a Cascade
.
openWritesThreshold
limits the number of open files to be output to.
- Parameters:
parent
- of type Tappartition
- of type StringsinkMode
- of type SinkModekeepParentOnDelete
- of type booleanopenWritesThreshold
- of type int
getCurrentIdentifier
protected String getCurrentIdentifier(FlowProcess<Properties> flowProcess)
- Specified by:
getCurrentIdentifier
in class BasePartitionTap<Properties,InputStream,OutputStream>
deleteResource
public boolean deleteResource(Properties conf)
throws IOException
- Overrides:
deleteResource
in class BasePartitionTap<Properties,InputStream,OutputStream>
- Throws:
IOException
createTupleEntrySchemeCollector
protected TupleEntrySchemeCollector createTupleEntrySchemeCollector(FlowProcess<Properties> flowProcess,
Tap parent,
String path,
long sequence)
throws IOException
- Specified by:
createTupleEntrySchemeCollector
in class BasePartitionTap<Properties,InputStream,OutputStream>
- Throws:
IOException
createTupleEntrySchemeIterator
protected TupleEntrySchemeIterator createTupleEntrySchemeIterator(FlowProcess<Properties> flowProcess,
Tap parent,
String path,
InputStream input)
throws FileNotFoundException
- Specified by:
createTupleEntrySchemeIterator
in class BasePartitionTap<Properties,InputStream,OutputStream>
- Throws:
FileNotFoundException
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