org.apache.flink.api.java.operators

Class AggregateOperator.AggregatingUdf<T extends Tuple>

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichGroupReduceFunction<T,T>

org.apache.flink.api.java.operators.AggregateOperator.AggregatingUdf<T>

All Implemented Interfaces:

Serializable, Function, GroupCombineFunction<T,T>, GroupReduceFunction<T,T>, RichFunction

Enclosing class:

AggregateOperator<IN>

@Internal
public static final class AggregateOperator.AggregatingUdf<T extends Tuple>
extends RichGroupReduceFunction<T,T>
implements GroupCombineFunction<T,T>

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AggregatingUdf(AggregationFunction<Object>[] aggFunctions, int[] fieldPositions)

Method Summary

Modifier and Type	Method and Description
void	combine(Iterable<T> records, Collector<T> out) The combine method, called (potentially multiple timed) with subgroups of elements.
void	open(Configuration parameters) Initialization method for the function.
void	reduce(Iterable<T> records, Collector<T> out) The reduce method.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, setRuntimeContext

Methods inherited from class java.lang.Object

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

Constructor Detail

AggregatingUdf

public AggregatingUdf(AggregationFunction<Object>[] aggFunctions,
                      int[] fieldPositions)

Method Detail

open

public void open(Configuration parameters)
          throws Exception

Description copied from interface: RichFunction

Initialization method for the function. It is called before the actual working methods (like map or join) and thus suitable for one time setup work. For functions that are part of an iteration, this method will be invoked at the beginning of each iteration superstep.

The configuration object passed to the function can be used for configuration and initialization. The configuration contains all parameters that were configured on the function in the program composition.

 public class MyMapper extends FilterFunction<String> {
 
     private String searchString;
     
     public void open(Configuration parameters) {
         this.searchString = parameters.getString("foo");
     }
     
     public boolean filter(String value) {
         return value.equals(searchString);
     }
 }
 

By default, this method does nothing.

Specified by:

open in interface RichFunction

Overrides:

open in class AbstractRichFunction

Parameters:

parameters - The configuration containing the parameters attached to the contract.

Throws:

Exception - Implementations may forward exceptions, which are caught by the runtime. When the runtime catches an exception, it aborts the task and lets the fail-over logic decide whether to retry the task execution.

See Also:

Configuration

reduce

public void reduce(Iterable<T> records,
                   Collector<T> out)

Description copied from interface: GroupReduceFunction

The reduce method. The function receives one call per group of elements.

Specified by:

reduce in interface GroupReduceFunction<T extends Tuple,T extends Tuple>

Specified by:

reduce in class RichGroupReduceFunction<T extends Tuple,T extends Tuple>

Parameters:

records - All records that belong to the given input key.

out - The collector to hand results to.

combine

public void combine(Iterable<T> records,
                    Collector<T> out)

Description copied from interface: GroupCombineFunction

The combine method, called (potentially multiple timed) with subgroups of elements.

Specified by:

combine in interface GroupCombineFunction<T extends Tuple,T extends Tuple>

Parameters:

records - The elements to be combined.

out - The collector to use to return values from the function.