Package org.apache.beam.sdk.transforms.windowing

Enum Class TimestampCombiner

java.lang.Object

java.lang.Enum<TimestampCombiner>

org.apache.beam.sdk.transforms.windowing.TimestampCombiner

All Implemented Interfaces:

Serializable, Comparable<TimestampCombiner>, Constable

public enum TimestampCombiner
extends Enum<TimestampCombiner>

Policies for combining timestamps that occur within a window.

In particular, these govern the timestamp on the output of a grouping transform such as GroupByKey or Combine.

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Enum

Enum.EnumDesc<E extends Enum<E>>

Enum Constant Summary

Enum Constants

Enum Constant	Description
EARLIEST	The policy of taking at the earliest of a set of timestamps.
END_OF_WINDOW	The policy of using the end of the window, regardless of input timestamps.
LATEST	The policy of taking the latest of a set of timestamps.

Method Summary

Modifier and Type	Method	Description
final Instant	assign(BoundedWindow intoWindow, Instant timestamp)	Shorthand for merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>) with just one element, to place it into the context of a window.
abstract Instant	combine(Iterable<? extends Instant> timestamps)	Combines the given times, which must be from the same window and must have been passed through merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>).
final Instant	combine(Instant... timestamps)	Varargs variant of combine(java.lang.Iterable<? extends org.joda.time.Instant>).
abstract boolean	dependsOnlyOnEarliestTimestamp()	Returns true if the result of combination of many output timestamps actually depends only on the earliest.
abstract boolean	dependsOnlyOnWindow()	Returns true if the result does not depend on what outputs were combined but only the window they are in.
abstract Instant	merge(BoundedWindow intoWindow, Iterable<? extends Instant> mergingTimestamps)	Merges the given timestamps, which may have originated in separate windows, into the context of the result window.
final Instant	merge(BoundedWindow intoWindow, Instant... timestamps)	Varargs variant of merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>).
static TimestampCombiner	valueOf(String name)	Returns the enum constant of this class with the specified name.
static TimestampCombiner[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, describeConstable, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

EARLIEST

public static final TimestampCombiner EARLIEST

The policy of taking at the earliest of a set of timestamps.

When used in windowed aggregations, the timestamps of non-late inputs will be combined after they are shifted by the WindowFn (to allow downstream watermark progress).

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

LATEST

public static final TimestampCombiner LATEST

The policy of taking the latest of a set of timestamps.

When used in windowed aggregations, the timestamps of non-late inputs will be combined after they are shifted by the WindowFn (to allow downstream watermark progress).

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

END_OF_WINDOW

public static final TimestampCombiner END_OF_WINDOW

The policy of using the end of the window, regardless of input timestamps.

When used in windowed aggregations, the timestamps of non-late inputs will be combined after they are shifted by the WindowFn (to allow downstream watermark progress).

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

Method Details

values

public static TimestampCombiner[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

an array containing the constants of this enum class, in the order they are declared

valueOf

public static TimestampCombiner valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum class has no constant with the specified name

NullPointerException - if the argument is null

combine

public abstract Instant combine(Iterable<? extends Instant> timestamps)

Combines the given times, which must be from the same window and must have been passed through merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>).

• combine must be commutative: combine(a, b).equals(combine(b, a)).
• combine must be associative: combine(a, combine(b, c)).equals(combine(combine(a, b), c)).

merge

public abstract Instant merge(BoundedWindow intoWindow,
 Iterable<? extends Instant> mergingTimestamps)

Merges the given timestamps, which may have originated in separate windows, into the context of the result window.

assign

public final Instant assign(BoundedWindow intoWindow,
 Instant timestamp)

Shorthand for merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>) with just one element, to place it into the context of a window.

For example, the END_OF_WINDOW policy moves the timestamp to the end of the window.

combine

public final Instant combine(Instant... timestamps)

Varargs variant of combine(java.lang.Iterable<? extends org.joda.time.Instant>).

merge

public final Instant merge(BoundedWindow intoWindow,
 Instant... timestamps)

Varargs variant of merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>).

dependsOnlyOnEarliestTimestamp

public abstract boolean dependsOnlyOnEarliestTimestamp()

Returns true if the result of combination of many output timestamps actually depends only on the earliest.

This may allow optimizations when it is very efficient to retrieve the earliest timestamp to be combined.

dependsOnlyOnWindow

public abstract boolean dependsOnlyOnWindow()

Returns true if the result does not depend on what outputs were combined but only the window they are in. The canonical example is if all timestamps are sure to be the end of the window.

This may allow optimizations, since it is typically very efficient to retrieve the window and combining output timestamps is not necessary.