Partitioner类中的参数numPartitions

Question

大师！

任何人都可以回答：Partitioner类中定义的参数numPartitions（此参数的值）？

Answer 1

这是为Map Reduce作业定义的缩减器数量

Answer 2

你是说那个意思吗？ numPartition in partition class。我刚刚使用了搜索there。

* @param numPartitions the total number of partitions. (as integer)
* [...] The total number of partitions 
* is the same as the number of reduce tasks for the job. 

Answer 3

在Driver类中，您将提到作业所需的减速器数量。该计数称为numPartion计数。 像：

job.setNumReduceTasks(4);