cascading.pipe.assembly
Class CountBy

java.lang.Object
  cascading.pipe.Pipe
      cascading.pipe.SubAssembly
          cascading.pipe.assembly.AggregateBy
              cascading.pipe.assembly.CountBy

All Implemented Interfaces:

FlowElement, Serializable

public class CountBy
extends AggregateBy

Class CountBy is used to count duplicates in a tuple stream.

Typically finding the count of a field in a tuple stream relies on a GroupBy and a Count Aggregator operation.

This SubAssembly also uses the CountBy.CountPartials AggregateBy.Functor to count field values before the GroupBy operator to reduce IO over the network.

This strategy is similar to using combiners, except no sorting or serialization is invoked and results in a much simpler mechanism.

The threshold value tells the underlying CountPartials functions how many unique key counts to accumulate in the LRU cache, before emitting the least recently used entry.

See Also:

AggregateBy, Serialized Form

Nested Class Summary

static class

CountBy.CountPartials Class CountPartials is a AggregateBy.Functor that is used to count observed duplicates from the tuple stream.

Nested classes/interfaces inherited from class cascading.pipe.assembly.AggregateBy

AggregateBy.CompositeFunction, AggregateBy.Flush, AggregateBy.Functor

Field Summary

Fields inherited from class cascading.pipe.assembly.AggregateBy

AGGREGATE_BY_THRESHOLD

Fields inherited from class cascading.pipe.Pipe

configDef, previous, stepConfigDef

Constructor Summary

CountBy(Fields countField)
Constructor CountBy creates a new CountBy instance.

CountBy(Pipe[] pipes, Fields groupingFields, Fields countField)
Constructor CountBy creates a new CountBy instance.

CountBy(Pipe[] pipes, Fields groupingFields, Fields countField, int threshold)
Constructor CountBy creates a new CountBy instance.

CountBy(Pipe pipe, Fields groupingFields, Fields countField)
Constructor CountBy creates a new CountBy instance.

CountBy(Pipe pipe, Fields groupingFields, Fields countField, int threshold)
Constructor CountBy creates a new CountBy instance.

CountBy(String name, Pipe[] pipes, Fields groupingFields, Fields countField)
Constructor CountBy creates a new CountBy instance.

CountBy(String name, Pipe[] pipes, Fields groupingFields, Fields countField, int threshold)
Constructor CountBy creates a new CountBy instance.

CountBy(String name, Pipe pipe, Fields groupingFields, Fields countField)
Constructor CountBy creates a new CountBy instance.

CountBy(String name, Pipe pipe, Fields groupingFields, Fields countField, int threshold)
Constructor CountBy creates a new CountBy instance.

Method Summary

Methods inherited from class cascading.pipe.assembly.AggregateBy

getAggregators, getArgumentFields, getFunctors, getGroupBy, initialize, initialize, verify

Methods inherited from class cascading.pipe.SubAssembly

getConfigDef, getName, getPrevious, getStepConfigDef, getTailNames, getTails, setTails, unwind

Methods inherited from class cascading.pipe.Pipe

equals, getHeads, getTrace, hasConfigDef, hashCode, hasStepConfigDef, isEquivalentTo, named, names, outgoingScopeFor, pipes, print, printInternal, resolveIncomingOperationArgumentFields, resolveIncomingOperationPassThroughFields, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

CountBy

@ConstructorProperties(value="countField")
public CountBy(Fields countField)

Constructor CountBy creates a new CountBy instance. Use this constructor when used with a AggregateBy instance.

Parameters:

countField - of type Fields

CountBy

@ConstructorProperties(value={"pipe","groupingFields","countField"})
public CountBy(Pipe pipe,
                                          Fields groupingFields,
                                          Fields countField)

Constructor CountBy creates a new CountBy instance.

Parameters:

pipe - of type Pipe

groupingFields - of type Fields

countField - of type Fields

CountBy

@ConstructorProperties(value={"pipe","groupingFields","countField","threshold"})
public CountBy(Pipe pipe,
                                          Fields groupingFields,
                                          Fields countField,
                                          int threshold)

Constructor CountBy creates a new CountBy instance.

Parameters:

pipe - of type Pipe

groupingFields - of type Fields

countField - fo type Fields

threshold - of type int

CountBy

@ConstructorProperties(value={"name","pipe","groupingFields","countField"})
public CountBy(String name,
                                          Pipe pipe,
                                          Fields groupingFields,
                                          Fields countField)

Constructor CountBy creates a new CountBy instance.

Parameters:

name - of type String

pipe - of type Pipe

groupingFields - of type Fields

countField - of type Fields

CountBy

@ConstructorProperties(value={"name","pipe","groupingFields","countField","threshold"})
public CountBy(String name,
                                          Pipe pipe,
                                          Fields groupingFields,
                                          Fields countField,
                                          int threshold)

Constructor CountBy creates a new CountBy instance.

Parameters:

name - of type String

pipe - of type Pipe

groupingFields - of type Fields

countField - of type Fields

threshold - of type int

CountBy

@ConstructorProperties(value={"pipes","groupingFields","countField"})
public CountBy(Pipe[] pipes,
                                          Fields groupingFields,
                                          Fields countField)

Constructor CountBy creates a new CountBy instance.

Parameters:

pipes - of type Pipe[]

groupingFields - of type Fields

countField - of type Fields

CountBy

@ConstructorProperties(value={"pipes","groupingFields","countField","threshold"})
public CountBy(Pipe[] pipes,
                                          Fields groupingFields,
                                          Fields countField,
                                          int threshold)

Constructor CountBy creates a new CountBy instance.

Parameters:

pipes - of type Pipe[]

groupingFields - of type Fields

countField - of type Fields

threshold - of type int

CountBy

@ConstructorProperties(value={"name","pipes","groupingFields","countField"})
public CountBy(String name,
                                          Pipe[] pipes,
                                          Fields groupingFields,
                                          Fields countField)

Constructor CountBy creates a new CountBy instance.

Parameters:

name - of type String

pipes - of type Pipe[]

groupingFields - of type Fields

countField - of type Fields

CountBy

@ConstructorProperties(value={"name","pipes","groupingFields","countField","threshold"})
public CountBy(String name,
                                          Pipe[] pipes,
                                          Fields groupingFields,
                                          Fields countField,
                                          int threshold)

Constructor CountBy creates a new CountBy instance.

Parameters:

name - of type String

pipes - of type Pipe[]

groupingFields - of type Fields

countField - of type Fields

threshold - of type int