/// <summary>
/// KeyBy()算子底层所采用的StreamPartitioner.
/// </summary>
/// <param name="record">the stream record.</param>
/// <returns>the sub-task id.</returns>
public override int SelectChannel(SerializationDelegate <StreamRecord <TElement> > record)
{
TKey key;
try
{
key = KeySelector.GetKey(record.Instance.Value);
}
catch (Exception e)
{
throw new RuntimeException($"Could not extract key from {record.Instance.Value}", e);
}
return(KeyGroupRangeAssignment.AssignKeyToParallelOperator(key, MaxParallelism, NumberOfChannels));
}