CoGroupedStreams (Flink : 2.0-SNAPSHOT API)

java.lang.Object
- org.apache.flink.streaming.api.datastream.CoGroupedStreams<T1,T2>

```
@Public
public class CoGroupedStreams<T1,T2>
extends Object
```
CoGroupedStreams represents two DataStreams that have been co-grouped. A streaming co-group operation is evaluated over elements in a window.
To finalize co-group operation you also need to specify a KeySelector for both the first and second input and a WindowAssigner.
Note: Right now, the groups are being built in memory so you need to ensure that they don't get too big. Otherwise the JVM might crash.
Example:
```
 DataStream<Tuple2<String, Integer>> one = ...;
 DataStream<Tuple2<String, Integer>> two = ...;

 DataStream<T> result = one.coGroup(two)
     .where(new MyFirstKeySelector())
     .equalTo(new MyFirstKeySelector())
     .window(TumblingEventTimeWindows.of(Duration.ofSeconds(5)))
     .apply(new MyCoGroupFunction());
 
```

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`CoGroupedStreams.TaggedUnion<T1,T2>`	Internal class for implementing tagged union co-group.
`static class`	`CoGroupedStreams.UnionSerializer<T1,T2>`	`TypeSerializer` for `CoGroupedStreams.TaggedUnion`.
`static class`	`CoGroupedStreams.UnionSerializerSnapshot<T1,T2>`	The `TypeSerializerSnapshot` for the `CoGroupedStreams.UnionSerializer`.
`class`	`CoGroupedStreams.Where<KEY>`	CoGrouped streams that have the key for one side defined.
`static class`	`CoGroupedStreams.WithWindow<T1,T2,KEY,W extends Window>`	A co-group operation that has `KeySelectors` defined for both inputs as well as a `WindowAssigner`.

Constructor Summary

Constructors
Constructor	Description
`CoGroupedStreams(DataStream<T1> input1, DataStream<T2> input2)`	Creates new CoGrouped data streams, which are the first step towards building a streaming co-group.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`<KEY> CoGroupedStreams.Where<KEY>`	`where(KeySelector<T1,KEY> keySelector)`	Specifies a `KeySelector` for elements from the first input.
`<KEY> CoGroupedStreams.Where<KEY>`	`where(KeySelector<T1,KEY> keySelector, TypeInformation<KEY> keyType)`	Specifies a `KeySelector` for elements from the first input with explicit type information.

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

- Constructor Detail
  - CoGroupedStreams
```
public CoGroupedStreams(DataStream<T1> input1,
                        DataStream<T2> input2)
```
    Creates new CoGrouped data streams, which are the first step towards building a streaming co-group.
    
    Parameters:
    
    input1 - The first data stream.
    
    input2 - The second data stream.
- Method Detail
  - where
```
public <KEY> CoGroupedStreams.Where<KEY> where(KeySelector<T1,KEY> keySelector)
```
    Specifies a KeySelector for elements from the first input.
    
    Parameters:
    
    keySelector - The KeySelector to be used for extracting the first input's key for partitioning.
  - where
```
public <KEY> CoGroupedStreams.Where<KEY> where(KeySelector<T1,KEY> keySelector,
                                               TypeInformation<KEY> keyType)
```
    Specifies a KeySelector for elements from the first input with explicit type information.
    
    Parameters:
    
    keySelector - The KeySelector to be used for extracting the first input's key for partitioning.
    
    keyType - The type information describing the key type.