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

Enum TimestampCombiner

java.lang.Object

java.lang.Enum<TimestampCombiner>

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

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<TimestampCombiner>

@Experimental(OUTPUT_TIME)
public enum TimestampCombiner
extends java.lang.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.

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
org.joda.time.Instant	assign(BoundedWindow intoWindow, org.joda.time.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 org.joda.time.Instant	combine(java.lang.Iterable<? extends org.joda.time.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>).
org.joda.time.Instant	combine(org.joda.time.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 org.joda.time.Instant	merge(BoundedWindow intoWindow, java.lang.Iterable<? extends org.joda.time.Instant> mergingTimestamps)	Merges the given timestamps, which may have originated in separate windows, into the context of the result window.
org.joda.time.Instant	merge(BoundedWindow intoWindow, org.joda.time.Instant... timestamps)	Varargs variant of merge(org.apache.beam.sdk.transforms.windowing.BoundedWindow, java.lang.Iterable<? extends org.joda.time.Instant>).
static TimestampCombiner	valueOf(java.lang.String name)	Returns the enum constant of this type with the specified name.
static TimestampCombiner[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

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 Detail

values

public static TimestampCombiner[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (TimestampCombiner c : TimestampCombiner.values())
    System.out.println(c);

Returns:

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

valueOf

public static TimestampCombiner valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (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:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

combine

public abstract org.joda.time.Instant combine(java.lang.Iterable<? extends org.joda.time.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 org.joda.time.Instant merge(BoundedWindow intoWindow,
                                            java.lang.Iterable<? extends org.joda.time.Instant> mergingTimestamps)

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

assign

public final org.joda.time.Instant assign(BoundedWindow intoWindow,
                                          org.joda.time.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 org.joda.time.Instant combine(org.joda.time.Instant... timestamps)

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

merge

public final org.joda.time.Instant merge(BoundedWindow intoWindow,
                                         org.joda.time.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.