地图减速器的数量减少 [英] Number of reducer in map reduce

问题描述

这意味着将创建三个分区。

在这种情况下，Reducer和reduce函数的运行时间是多少？

$ b

$ b

解决方案

如果你设置了3个reducer，它们将全部运行。但是，如果您在大多数中只有两个键，那么两个减速器实际上会接收要处理的数据。

I have set 3 reducer in driver class in MR.

it means three partitions will be created..

but mapper is emiting only two unique key say male and female.

In this case, how times Reducer and reduce functions will run?

解决方案

If you set 3 reducers they will all run. However, if you only have two keys at most two of the reducers will actually receive data to process.

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