org.apache.beam.sdk.transforms.windowing

Class OutputTimeFns

java.lang.Object

org.apache.beam.sdk.transforms.windowing.OutputTimeFns

@Experimental(value=OUTPUT_TIME)
public class OutputTimeFns
extends Object

(Experimental) Static utility methods and provided implementations for OutputTimeFn.

Constructor Summary

Constructors

Constructor and Description
OutputTimeFns()

Method Summary

Modifier and Type	Method and Description
static Instant	combineOutputTimes(OutputTimeFn<?> outputTimeFn, Iterable<? extends Instant> outputTimes) Applies the given OutputTimeFn to the given output times, obtaining the output time for a value computed.
static OutputTimeFn<BoundedWindow>	outputAtEarliestInputTimestamp() The policy of outputting at the earliest of the input timestamps for non-late input data that led to a computed value.
static OutputTimeFn<BoundedWindow>	outputAtEndOfWindow() The policy of outputting with timestamps at the end of the window.
static OutputTimeFn<BoundedWindow>	outputAtLatestInputTimestamp() The policy of holding the watermark to the latest of the input timestamps for non-late input data that led to a computed value.

Methods inherited from class java.lang.Object

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

Constructor Detail

OutputTimeFns

public OutputTimeFns()

Method Detail

outputAtEarliestInputTimestamp

public static OutputTimeFn<BoundedWindow> outputAtEarliestInputTimestamp()

The policy of outputting at the earliest of the input timestamps for non-late input data that led to a computed value.

For example, suppose v₁ through v_n are all on-time elements being aggregated via some function f into f(v₁, ..., v_n. When emitted, the output timestamp of the result will be the earliest of the event time timestamps

If data arrives late, it has no effect on the output timestamp.

outputAtLatestInputTimestamp

public static OutputTimeFn<BoundedWindow> outputAtLatestInputTimestamp()

The policy of holding the watermark to the latest of the input timestamps for non-late input data that led to a computed value.

For example, suppose v₁ through v_n are all on-time elements being aggregated via some function f into f(v₁, ..., v_n. When emitted, the output timestamp of the result will be the latest of the event time timestamps

If data arrives late, it has no effect on the output timestamp.

outputAtEndOfWindow

public static OutputTimeFn<BoundedWindow> outputAtEndOfWindow()

The policy of outputting with timestamps at the end of the window.

Note that this output timestamp depends only on the window. See {#link dependsOnlyOnWindow()}.

When windows merge, instead of using OutputTimeFn.combine(org.joda.time.Instant, org.joda.time.Instant) to obtain an output timestamp for the results in the new window, it is mandatory to obtain a new output timestamp from OutputTimeFn.assignOutputTime(org.joda.time.Instant, W) with the new window and an arbitrary timestamp (because it is guaranteed that the timestamp is irrelevant).

For non-merging window functions, this OutputTimeFn works transparently.

combineOutputTimes

public static Instant combineOutputTimes(OutputTimeFn<?> outputTimeFn,
                                         Iterable<? extends Instant> outputTimes)

Applies the given OutputTimeFn to the given output times, obtaining the output time for a value computed. See OutputTimeFn.combine(org.joda.time.Instant, org.joda.time.Instant) for a full specification.

Throws:

IllegalArgumentException - if outputTimes is empty.