WindowMappingFn (core 2.44.0 API)

java.lang.Object
- org.apache.beam.sdk.transforms.windowing.WindowMappingFn<TargetWindowT>

All Implemented Interfaces:

java.io.Serializable
```
@Experimental
public abstract class WindowMappingFn<TargetWindowT extends BoundedWindow>
extends java.lang.Object
implements java.io.Serializable
```
Experimental! This will be ready for users eventually, but should be considered internal for now. No backwards compatibility guarantees.
A function that takes the windows of elements in a main input and maps them to the appropriate window in a PCollectionView consumed as a side input.

See Also:

Serialized Form

Constructor Summary

Constructors
Modifier	Constructor	Description
`protected`	`WindowMappingFn()`	Create a new `WindowMappingFn` with `zero` maximum lookback.
`protected`	`WindowMappingFn(org.joda.time.Duration maximumLookback)`	Create a new `WindowMappingFn` with the specified maximum lookback.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract TargetWindowT`	`getSideInputWindow(BoundedWindow mainWindow)`	Returns the window of the side input corresponding to the given window of the main input.
`org.joda.time.Duration`	`maximumLookback()`	The maximum distance between the end of any main input window `mainWindow` and the end of the side input window returned by `getSideInputWindow(BoundedWindow)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - WindowMappingFn
```
protected WindowMappingFn()
```
    Create a new WindowMappingFn with zero maximum lookback.
  - WindowMappingFn
```
protected WindowMappingFn(org.joda.time.Duration maximumLookback)
```
    Create a new WindowMappingFn with the specified maximum lookback.
- Method Detail
  - getSideInputWindow
```
public abstract TargetWindowT getSideInputWindow(BoundedWindow mainWindow)
```
    Returns the window of the side input corresponding to the given window of the main input.
  - maximumLookback
```
public final org.joda.time.Duration maximumLookback()
```
    The maximum distance between the end of any main input window mainWindow and the end of the side input window returned by getSideInputWindow(BoundedWindow)
    A side input window w becomes unreachable when the input watermarks for all consumers surpasses the timestamp:
    (end of side input window) + (maximum lookback) + (main input allowed lateness).
    At this point, every main input window that could map to w is expired.