Why mapPartitionsWithIndex cause a shuffle in Spark? -


i'm new in spark. i'm checking shuffling issues in test application , don't know why in program mappartitionswithindex method cause shuffle! can see in picture initial rdd has 2 16mb partition , shuffle write 49.8 mb. know map or mappartition or mappartitionswithindex not shuffling transformation groupbykey see cause shuffle in spark. why?

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i think performing join/group operation after mappartitionswithindex , causing shuffle.

you can establish modifying code.

current code

val rdd = inputrdd1.mappartitionswithindex(....) val outrdd = rdd.join(inputrdd2)

modified code

val rdd = inputrdd1.mappartitionswithindex(....) println(rdd.count)

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