AsyncStream (Pinot Query Runtime 1.0.0 API)

Type Parameters:

E - The type of the elements, usually a TransferableBlock
```
public interface AsyncStream<E>
```
An interface that represents an abstract asynchronous stream of elements that can be consumed. These streams are designed to be consumed by a single thread and do not support null elements.

Nested Class Summary

Nested Classes
Modifier and Type Interface Description

static interface AsyncStream.OnNewData

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`addOnNewDataListener(AsyncStream.OnNewData onNewData)`	Registers a callback.
`void`	`cancel()`	Cancels this stream.
`Object`	`getId()`	The id of the stream.
`E`	`poll()`	Reads the next element, if there is any to read.

- Method Detail
  - getId
```
Object getId()
```
    The id of the stream. Mostly used for logging. Implementations of this method must be thread safe.
  - poll
```
@Nullable
E poll()
```
    Reads the next element, if there is any to read. Otherwise it returns null. Calling this method before setting a callback with addOnNewDataListener(OnNewData) is illegal as it may imply losing information. Only the consumer thread can call this method.
    
    Returns:
    
    the next element to consume, which cannot be null, or null if there is no element ready yet.
  - addOnNewDataListener
```
void addOnNewDataListener(AsyncStream.OnNewData onNewData)
```
    Registers a callback. Once set, the callback cannot be changed. In order to call poll(), a callback has to be registered. Only the consumer thread can call this method.
    
    Parameters:
    
    onNewData -
  - cancel
```
void cancel()
```
    Cancels this stream. Only the consumer thread can call this method.