org.apache.flink.table.runtime.operators.window.assigners

Class WindowAssigner<W extends Window>

java.lang.Object

org.apache.flink.table.runtime.operators.window.assigners.WindowAssigner<W>

Type Parameters:

W - The type of Window that this assigner assigns.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

CountSlidingWindowAssigner, CountTumblingWindowAssigner, MergingWindowAssigner, PanedWindowAssigner, TumblingWindowAssigner

public abstract class WindowAssigner<W extends Window>
extends Object
implements Serializable

A WindowAssigner assigns zero or more Windows to an element.

In a window operation, elements are grouped by their key (if available) and by the windows to which it was assigned. The set of elements with the same key and window is called a pane. When a Trigger decides that a certain pane should fire the window to produce output elements for that pane.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
WindowAssigner()

Method Summary

Modifier and Type	Method and Description
abstract Collection<W>	assignWindows(RowData element, long timestamp) Given the timestamp and element, returns the set of windows into which it should be placed.
abstract TypeSerializer<W>	getWindowSerializer(ExecutionConfig executionConfig) Returns a TypeSerializer for serializing windows that are assigned by this WindowAssigner.
abstract boolean	isEventTime() Returns true if elements are assigned to windows based on event time, false otherwise.
void	open(InternalWindowProcessFunction.Context<?,W> ctx) Initialization method for the function.
abstract String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

WindowAssigner

public WindowAssigner()

Method Detail

open

public void open(InternalWindowProcessFunction.Context<?,W> ctx)
          throws Exception

Initialization method for the function. It is called before the actual working methods.

Throws:

Exception

assignWindows

public abstract Collection<W> assignWindows(RowData element,
                                            long timestamp)
                                     throws IOException

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

Parameters:

element - The element to which windows should be assigned.

timestamp - The timestamp of the element when isEventTime() returns true, or the current system time when isEventTime() returns false. The timestamp value is mapping to UTC milliseconds for splitting windows simply.

Throws:

IOException

getWindowSerializer

public abstract TypeSerializer<W> getWindowSerializer(ExecutionConfig executionConfig)

Returns a TypeSerializer for serializing windows that are assigned by this WindowAssigner.

isEventTime

public abstract boolean isEventTime()

Returns true if elements are assigned to windows based on event time, false otherwise.

toString

public abstract String toString()

Overrides:

toString in class Object