Shulou(Shulou.com)06/02 Report--

This article is to share with you about how to achieve secondary sorting in MapReduce, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

I. demand analysis

The requirement for the secondary sorting of MR indicates that during the mapreduce operation, the shuffle phase will sort according to the key value several times. However, after shuffle is grouped, the order of values sequences with the same key values is uncertain (see figure below). If you want the value value to be sorted at this time, this requirement is the second sort.

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