cascading.nested.core

Interface NestedAggregate<Node,Context>

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

AverageDoubleNestedAggregate, BaseNumberNestedAggregate, SimpleNestedAggregate, SumDoubleNestedAggregate, SumLongNestedAggregate

public interface NestedAggregate<Node,Context>
extends java.io.Serializable

Interface NestedAggregate provides a basic abstraction for aggregating set of values collected from a set of parent objects.

See SimpleNestedAggregate for a convenient base implementation.

See Also:

NestedGetAllAggregateFunction

Method Summary

Modifier and Type	Method and Description
void	aggregate(Context context, Node node) This method receives each collected value to be applied to the current aggregation.
cascading.tuple.Tuple	complete(Context context) This method completes the aggregate operation and insert the results into a Tuple instance.
Context	createContext(cascading.tuple.type.CoercibleType<Node> nestedCoercibleType)
cascading.tuple.Fields	getFieldDeclaration()
Context	resetContext(Context context) This method is called after complete(Object) so that any resources can be freed and the result context instance can be used in the next aggregation.

Method Detail

getFieldDeclaration

cascading.tuple.Fields getFieldDeclaration()

Returns:

the fields this aggregate function will return

createContext

Context createContext(cascading.tuple.type.CoercibleType<Node> nestedCoercibleType)

Returns:

a new function specific context object

aggregate

void aggregate(Context context,
               Node node)

This method receives each collected value to be applied to the current aggregation.

Parameters:

context - the context object created by createContext(CoercibleType)

node - the Node container object that should be aggregated

complete

cascading.tuple.Tuple complete(Context context)

This method completes the aggregate operation and insert the results into a Tuple instance.

Note the Tuple may be created (indirectly) by the createContext(CoercibleType) method and reused.

Parameters:

context - the context object created by createContext(CoercibleType)

Returns:

a Tuple containing the aggregate value(s), the Tuple may be reused

resetContext

Context resetContext(Context context)

This method is called after complete(Object) so that any resources can be freed and the result context instance can be used in the next aggregation.

Parameters:

context - the context object created by createContext(CoercibleType)

Returns:

either a cleared or new context instance to be used in further aggregations