com.asakusafw.vocabulary.flow.processor

Enum InputBuffer

java.lang.Object

java.lang.Enum<InputBuffer>

com.asakusafw.vocabulary.flow.processor.InputBuffer

All Implemented Interfaces:

FlowElementAttribute, Serializable, Comparable<InputBuffer>

public enum InputBuffer
extends Enum<InputBuffer>
implements FlowElementAttribute

Represents buffering strategies of list-style operator inputs.

Since:

0.2.0

Enum Constant Summary

Enum Constants

Enum Constant and Description
ESCAPE Builds a buffer onto the JVM heap, and will escape it to disks each time the buffer is full.
EXPAND Builds a buffer onto the JVM heap, and will expand its area each time the buffer is full.

Method Summary

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

Methods inherited from interface com.asakusafw.vocabulary.flow.graph.FlowElementAttribute

getDeclaringClass

Enum Constant Detail

EXPAND

public static final InputBuffer EXPAND

Builds a buffer onto the JVM heap, and will expand its area each time the buffer is full. This strategy is relatively fast, but it is limited by JVM heap constraints. For example, it is hard to handle a large input group for this strategy.

ESCAPE

public static final InputBuffer ESCAPE

Builds a buffer onto the JVM heap, and will escape it to disks each time the buffer is full. With this strategy, the operator can handle a large input group, but clients retrieve only one by one object from it (old objects may by changed when retrieving another one). Additionally, even if an object in the list was changed, its change may be lost when another object was retrieved from the list. For example, the operations are not guaranteed in the following case:

@CoGroup(inputBuffer = InputBuffer.ESCAPE)
public void invalid(@Key(...) List<Hoge> list, Result<Hoge> result) {
    // contents of 'a' is not guaranteed after 'list.get(1)'
    Hoge a = list.get(0);
    Hoge b = list.get(1);

    // the change may be lost after 'list.get(2)'
    b.setValue(100);
    list.get(2);
}

In such the case, application developers should create a copy of the object:

Hoge a = new Hoge();
Hoge b = new Hoge();

@CoGroup(inputBuffer = InputBuffer.ESCAPE)
public void invalid(@Key(...) List<Hoge> list, Result<Hoge> result) {
    a.copyFrom(list.get(0));
    b.copyFrom(list.get(1));
    b.setValue(100);
    list.get(2);
    ...
}

Note that, copy is not necessary if objects are only used one by one:

@CoGroup(inputBuffer = InputBuffer.ESCAPE)
public void invalid(@Key(...) List<Hoge> list, Result<Hoge> result) {
    for (Hoge hoge : list) {
        hoge.setValue(100);
        result.add(hoge);
    }
}

See Also:

Once, Spill

Method Detail

values

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

Returns:

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

valueOf

public static InputBuffer 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