Package org.apache.flink.api.common.operators.base

Enum ReduceOperatorBase.CombineHint

java.lang.Object

java.lang.Enum<ReduceOperatorBase.CombineHint>

org.apache.flink.api.common.operators.base.ReduceOperatorBase.CombineHint

All Implemented Interfaces:

Serializable, Comparable<ReduceOperatorBase.CombineHint>

Enclosing class:

ReduceOperatorBase<T,FT extends ReduceFunction<T>>

public static enum ReduceOperatorBase.CombineHint
extends Enum<ReduceOperatorBase.CombineHint>

An enumeration of hints, optionally usable to tell the system exactly how to execute the combiner phase of a reduce. (Note: The final reduce phase (after combining) is currently always executed by a sort-based strategy.)

Enum Constant Summary

Enum Constants

Enum Constant	Description
HASH	Use a hash-based strategy.
NONE	Disable the use of a combiner.
OPTIMIZER_CHOOSES	Leave the choice how to do the combine to the optimizer.
SORT	Use a sort-based strategy.

Method Summary

Modifier and Type	Method	Description
static ReduceOperatorBase.CombineHint	valueOf(String name)	Returns the enum constant of this type with the specified name.
static ReduceOperatorBase.CombineHint[]	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

OPTIMIZER_CHOOSES

public static final ReduceOperatorBase.CombineHint OPTIMIZER_CHOOSES

Leave the choice how to do the combine to the optimizer. (This currently defaults to SORT.)

SORT

public static final ReduceOperatorBase.CombineHint SORT

Use a sort-based strategy.

HASH

public static final ReduceOperatorBase.CombineHint HASH

Use a hash-based strategy. This should be faster in most cases, especially if the number of different keys is small compared to the number of input elements (eg. 1/10).

NONE

public static final ReduceOperatorBase.CombineHint NONE

Disable the use of a combiner.

Method Detail

values

public static ReduceOperatorBase.CombineHint[] 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 (ReduceOperatorBase.CombineHint c : ReduceOperatorBase.CombineHint.values())
    System.out.println(c);

Returns:

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

valueOf

public static ReduceOperatorBase.CombineHint valueOf(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:

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

NullPointerException - if the argument is null