HeapPriorityQueue (Flink : Runtime 2.1.0 API)

java.lang.Object
- org.apache.flink.streaming.runtime.watermarkstatus.HeapPriorityQueue<T>

Type Parameters:

T - type of the contained elements.
```
public class HeapPriorityQueue<T extends HeapPriorityQueue.HeapPriorityQueueElement>
extends Object
```
This class has similar functions with HeapPriorityQueue. It is introduced as the replacement of HeapPriorityQueue to be used in StatusWatermarkValve, to avoid affecting the performance of memory state backend.
The reason why the performance of memory state backend will be affected if we reuse the HeapPriorityQueue: In some scenarios, the HeapPriorityQueueElement will only have one implementation(used by memory state backend), which allows the jvm to inline its methods(getInternalIndex, setInternalIndex). If we reuse it in StatusWatermarkValve, it will cause it to have multiple implementations. Once there are multiple implementations, its methods will be difficult to be inlined by jvm, which will result in poor performance of memory state backend.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static interface`	`HeapPriorityQueue.HeapPriorityQueueElement`	Interface for objects that can be managed by a `HeapPriorityQueue`.
`static interface`	`HeapPriorityQueue.PriorityComparator<T>`	This interface works similar to `Comparable` and is used to prioritize between two objects.

Constructor Summary

Constructors
Constructor	Description
`HeapPriorityQueue(HeapPriorityQueue.PriorityComparator<T> elementPriorityComparator, int minimumCapacity)`	Creates an empty `HeapPriorityQueue` with the requested initial capacity.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`add(T toAdd)`
`void`	`adjustModifiedElement(T element)`
`void`	`clear()`	Clears the queue.
`boolean`	`isEmpty()`
`T`	`peek()`
`T`	`poll()`
`boolean`	`remove(T toRemove)`
`int`	`size()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- HeapPriorityQueue
```
public HeapPriorityQueue(@Nonnull
                         HeapPriorityQueue.PriorityComparator<T> elementPriorityComparator,
                         @Nonnegative
                         int minimumCapacity)
```
  Creates an empty HeapPriorityQueue with the requested initial capacity.
  
  Parameters:
  
  elementPriorityComparator - comparator for the priority of contained elements.
  
  minimumCapacity - the minimum and initial capacity of this priority queue.

Method Detail

adjustModifiedElement

public void adjustModifiedElement(@Nonnull
                                  T element)

poll
```
@Nullable
public T poll()
```

peek
```
@Nullable
public T peek()
```

add

public boolean add(@Nonnull
                   T toAdd)

remove

public boolean remove(@Nonnull
                      T toRemove)

isEmpty
```
public boolean isEmpty()
```

size
```
public int size()
```

clear
```
public void clear()
```
Clears the queue.