org.apache.kafka.streams.kstream

Class JoinWindows

java.lang.Object

org.apache.kafka.streams.kstream.Windows<TimeWindow>

org.apache.kafka.streams.kstream.JoinWindows

public class JoinWindows
extends Windows<TimeWindow>

The window specifications used for joins.

A JoinWindows instance defines a join over two stream on the same key and a maximum time difference. In SQL-style you would express this join as

     SELECT * FROM stream1, stream2
     WHERE
       stream1.key = stream2.key
       AND
       stream2.ts - before <= stream1.ts <= stream2.ts + after
 

There are three different window configuration supported:

• before = after = time-difference
• before = 0 and after = time-difference
• before = time-difference and after = 0

A join is symmetric in the sense, that a join specification on the first stream returns the same result record as a join specification on the second stream with flipped before and after values.

Both values (before and after) must not result in an "inverse" window, i.e., lower-interval-bound must not be larger than upper-interval.bound.

Field Summary

Fields

Modifier and Type	Field and Description
long	after Maximum time difference for tuples that are after the join tuple.
long	before Maximum time difference for tuples that are before the join tuple.

Fields inherited from class org.apache.kafka.streams.kstream.Windows

name, segments

Method Summary

Methods

Modifier and Type	Method and Description
JoinWindows	after(long timeDifference) Specifies that records of the same key are joinable if their timestamps are within the join window interval, and if the timestamp of a record from the secondary stream is later than or equal to the timestamp of a record from the first stream.
JoinWindows	before(long timeDifference) Specifies that records of the same key are joinable if their timestamps are within the join window interval, and if the timestamp of a record from the secondary stream is earlier than or equal to the timestamp of a record from the first stream.
boolean	equals(Object o)
int	hashCode()
static JoinWindows	of(String name) Specifies that records of the same key are joinable if their timestamps are equal.
Map<Long,TimeWindow>	windowsFor(long timestamp) Not supported by JoinWindows.
JoinWindows	with(long timeDifference) Specifies that records of the same key are joinable if their timestamps are within timeDifference.

Methods inherited from class org.apache.kafka.streams.kstream.Windows

maintainMs, name, segments, until

Methods inherited from class java.lang.Object

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

Field Detail

before

public final long before

Maximum time difference for tuples that are before the join tuple.

after

public final long after

Maximum time difference for tuples that are after the join tuple.

Method Detail

of

public static JoinWindows of(String name)

Specifies that records of the same key are joinable if their timestamps are equal.

Parameters:

name - The name of the window. Must not be null or empty.

with

public JoinWindows with(long timeDifference)

Specifies that records of the same key are joinable if their timestamps are within timeDifference.

Parameters:

timeDifference - join window interval (must not be negative)

before

public JoinWindows before(long timeDifference)

Specifies that records of the same key are joinable if their timestamps are within the join window interval, and if the timestamp of a record from the secondary stream is earlier than or equal to the timestamp of a record from the first stream.

Parameters:

timeDifference - join window interval

after

public JoinWindows after(long timeDifference)

Specifies that records of the same key are joinable if their timestamps are within the join window interval, and if the timestamp of a record from the secondary stream is later than or equal to the timestamp of a record from the first stream.

Parameters:

timeDifference - join window interval

windowsFor

public Map<Long,TimeWindow> windowsFor(long timestamp)

Not supported by JoinWindows. Throws UnsupportedOperationException.

Specified by:

windowsFor in class Windows<TimeWindow>

Parameters:

timestamp - the timestamp window should get created for

Returns:

a map of windowStartTimestamp -> Window entries

equals

public final boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object