Package stream.nebula.operators

Class KeyedWindowOperator

java.lang.Object

stream.nebula.operators.Operator

stream.nebula.operators.KeyedWindowOperator

Direct Known Subclasses:

WindowOperator

public class KeyedWindowOperator
extends Operator

Base class to encode a Query.window(stream.nebula.operators.window.WindowDefinition) operation.

This class stores the data to define a window, i.e., the WindowDefinition (getWindowDefinition()) , a list of attribute names on which the window is grouped (getKeyFields()), and a list of Aggregation functions (getAggregations()).

This class and its subtype WindowOperator follow the builder pattern. Query.window(stream.nebula.operators.window.WindowDefinition) returns a WindowOperator instance on which the user can either call apply(stream.nebula.operators.Aggregation...) or WindowOperator.byKey(java.lang.String...). apply(stream.nebula.operators.Aggregation...) finishes the specification of the window and returns the original Query instance. WindowOperator.byKey(java.lang.String...) sets the grouping attributes of the window and returns a KeyedWindowOperator on which the user has to call apply(stream.nebula.operators.Aggregation...) to finish the specification of the window.

Field Summary

Fields inherited from class stream.nebula.operators.Operator

childOperator

Constructor Summary

Constructors

Constructor	Description
KeyedWindowOperator(@NonNull Operator childOperator, @NonNull WindowDefinition windowDefinition, @NonNull Query query)	Create a new KeyedWindowOperator and set the window definition to define the extent of the window.

Method Summary

Modifier and Type	Method	Description
Query	apply(Aggregation... aggregations)	Set the aggregation functions for this window.
java.util.List<Aggregation>	getAggregations()	Access the window aggregation functions.
java.util.List<java.lang.String>	getKeyFields()	Access the attribute names on which the window is grouped.
WindowDefinition	getWindowDefinition()	Access the window definition.
protected void	setKeyFields(@NonNull java.util.List<java.lang.String> keyFields)	Set the stream attribute names on which the window is grouped.

Methods inherited from class stream.nebula.operators.Operator

getChildOperator

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KeyedWindowOperator

public KeyedWindowOperator(@NonNull Operator childOperator,
                           @NonNull WindowDefinition windowDefinition,
                           @NonNull Query query)
                    throws java.lang.IllegalArgumentException

Create a new KeyedWindowOperator and set the window definition to define the extent of the window.

Parameters:

childOperator - The previous operator in the operator chain of query.

windowDefinition - The window definition.

query - The Query instance on which Query.window(stream.nebula.operators.window.WindowDefinition) was called.

Throws:

java.lang.IllegalArgumentException - If windowDefinition is null.

Method Detail

apply

public Query apply(Aggregation... aggregations)
            throws java.lang.IllegalArgumentException

Set the aggregation functions for this window.

Parameters:

aggregations - A variable number of Aggregation instances.

Returns:

The original Query instance on which Query.window(stream.nebula.operators.window.WindowDefinition) was called.

Throws:

java.lang.IllegalArgumentException - If aggregations is null or empty, or if an element of aggregations is null.

getWindowDefinition

public WindowDefinition getWindowDefinition()

Access the window definition.

Returns:

The window definition.

setKeyFields

protected void setKeyFields(@NonNull java.util.List<java.lang.String> keyFields)

Set the stream attribute names on which the window is grouped.

This method is protected so that it can only be called in WindowOperator but not from the Query API.

Parameters:

keyFields - The grouping key names.

getKeyFields

public java.util.List<java.lang.String> getKeyFields()

Access the attribute names on which the window is grouped.

Returns:

The grouping key names.

getAggregations

public java.util.List<Aggregation> getAggregations()

Access the window aggregation functions.

Returns:

A list of Aggregation instances for this window.