com.google.cloud.dataflow.sdk.transforms.windowing

Class WindowingFn<T,W extends BoundedWindow>

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.windowing.WindowingFn<T,W>

Type Parameters:

T - type of elements being windowed

W - BoundedWindow subclass used to represent the windows used by this WindowingFn

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

InvalidWindowingFn, NonMergingWindowingFn, Sessions

public abstract class WindowingFn<T,W extends BoundedWindow>
extends java.lang.Object
implements java.io.Serializable

The argument to the Window transform used to assign elements into windows and to determine how windows are merged. See Window for more information on how WindowingFns are used and for a library of predefined WindowingFns.

Users will generally want to use the predefined WindowingFns, but it is also possible to create new subclasses. TODO: Describe how to properly create WindowingFns.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	WindowingFn.AssignContext Information available when running assignWindows(com.google.cloud.dataflow.sdk.transforms.windowing.WindowingFn<T, W>.AssignContext).
class	WindowingFn.MergeContext Information available when running mergeWindows(com.google.cloud.dataflow.sdk.transforms.windowing.WindowingFn<T, W>.MergeContext).

Constructor Summary

Constructors

Constructor and Description
WindowingFn()

Method Summary

Methods

Modifier and Type	Method and Description
abstract java.util.Collection<W>	assignWindows(WindowingFn.AssignContext c) Given a timestamp and element, returns the set of windows into which it should be placed.
abstract boolean	isCompatible(WindowingFn<?,?> other) Returns whether this performs the same merging as the given WindowingFn.
abstract void	mergeWindows(WindowingFn.MergeContext c) Does whatever merging of windows is necessary.
abstract Coder<W>	windowCoder() Returns the Coder used for serializing the windows used by this windowingFn.

Methods inherited from class java.lang.Object

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

Constructor Detail

WindowingFn

public WindowingFn()

Method Detail

assignWindows

public abstract java.util.Collection<W> assignWindows(WindowingFn.AssignContext c)
                                                                     throws java.lang.Exception

Given a timestamp and element, returns the set of windows into which it should be placed.

Throws:

java.lang.Exception

mergeWindows

public abstract void mergeWindows(WindowingFn.MergeContext c)
                           throws java.lang.Exception

Does whatever merging of windows is necessary.

See MergeOverlappingIntervalWindows.mergeWindows(com.google.cloud.dataflow.sdk.transforms.windowing.WindowingFn<?, com.google.cloud.dataflow.sdk.transforms.windowing.IntervalWindow>.MergeContext) for an example of how to override this method.

Throws:

java.lang.Exception

isCompatible

public abstract boolean isCompatible(WindowingFn<?,?> other)

Returns whether this performs the same merging as the given WindowingFn.

windowCoder

public abstract Coder<W> windowCoder()

Returns the Coder used for serializing the windows used by this windowingFn.