org.apache.flink.streaming.api.functions.co

Interface CoReduceFunction<IN1,IN2,OUT>

Type Parameters:

IN1 - Type of the first input.

IN2 - Type of the second input.

OUT - Output type.

All Superinterfaces:

org.apache.flink.api.common.functions.Function, Serializable

All Known Implementing Classes:

RichCoReduceFunction

public interface CoReduceFunction<IN1,IN2,OUT>
extends org.apache.flink.api.common.functions.Function, Serializable

The CoReduceFunction interface represents a Reduce transformation with two different input streams. The reduce1 function combine groups of elements of the first input with the same key to a single value, while reduce2 combine groups of elements of the second input with the same key to a single value. Each produced values are mapped to the same type by map1 and map2, respectively, to form one output stream. The basic syntax for using a grouped ReduceFunction is as follows:

 

 ConnectedDataStream input = ...;
 
 ConnectedDataStream result = input.groupBy(keyPosition1, keyPosition2)
          .reduce(new MyCoReduceFunction(), keyPosition1, keyPosition2).addSink(...);
 
 

Method Summary

Modifier and Type	Method and Description
OUT	map1(IN1 value) Maps the reduced first input to the output type.
OUT	map2(IN2 value) Maps the reduced second input to the output type.
IN1	reduce1(IN1 value1, IN1 value2) The core method of CoReduceFunction, combining two values of the first input into one value of the same type.
IN2	reduce2(IN2 value1, IN2 value2) The core method of ReduceFunction, combining two values of the second input into one value of the same type.

Method Detail

reduce1

IN1 reduce1(IN1 value1,
            IN1 value2)
     throws Exception

The core method of CoReduceFunction, combining two values of the first input into one value of the same type. The reduce1 function is consecutively applied to all values of a group until only a single value remains.

Parameters:

value1 - The first value to combine.

value2 - The second value to combine.

Returns:

The combined value of both input values.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.

reduce2

IN2 reduce2(IN2 value1,
            IN2 value2)
     throws Exception

The core method of ReduceFunction, combining two values of the second input into one value of the same type. The reduce2 function is consecutively applied to all values of a group until only a single value remains.

Parameters:

value1 - The first value to combine.

value2 - The second value to combine.

Returns:

The combined value of both input values.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.

map1

OUT map1(IN1 value)
  throws Exception

Maps the reduced first input to the output type.

Parameters:

value - Type of the first input.

Returns:

the output type.

Throws:

Exception

map2

OUT map2(IN2 value)
  throws Exception

Maps the reduced second input to the output type.

Parameters:

value - Type of the second input.

Returns:

the output type.

Throws:

Exception