com.asakusafw.vocabulary.model

Annotation Type Spill

@Target(value=PARAMETER)
 @Retention(value=RUNTIME)
 @Documented
public @interface Spill

An annotation represents which the annotated element can spill its contents into backing store. This can appear with the following elements:

• Input parameter of CoGroup and GroupSort operator methods. A parameter with this annotation may have too many elements in its list. In such the case, we spill the elements into a temporary file, and flush the elements from the Java heap. With this annotation, obtaining elements from the sequence will change the previously obtained object. For example, the operations are not guaranteed in the following case:

  
  @CoGroup
  public void invalid(@Key(...) @Spill List<Hoge> input, Result<Hoge> result) {
      Hoge a = input.get(0);
      Hoge b = input.get(1); // this operation may break out contents of 'a'
      ...
  }
  

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

  
  final Hoge a = new Hoge();
  final Hoge b = new Hoge();
  
  @CoGroup
  public void invalid(@Key(...) @Spill List<Hoge> input, Result<Hoge> result) {
      a.copyFrom(input.get(0)); // take a copy
      b.copyFrom(input.get(1));
      ...
  }
  

Since:

0.9.1

See Also:

Once