Detailed introduction to the combineByKey operator in Spark

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1. Detailed introduction to the combineByKey operator in Spark

In the previous blog posts, we explained reduceByKey, aggregateByKey, foldByKeyand , respectively. This article will explain a more general aggregation function combineByKey. In fact, the above-mentioned functions all call this function at the bottom layer, which is more flexible.

1. Function introduction

combineByKeyIt is a transformation operator (Transformation Operator) in Spark, which is used to aggregate the values ​​in the RDD of key-value pair type. It provides a more flexible aggregation method, allowing you to perform local aggregation for the value of each key, and use different functions in the local aggregation and global aggregation stages to generate a new key-value pair type RDD.