Remove Empty Partitions from Spark RDD

问题:

I am fetching data from HDFS and storing it in a Spark RDD. Spark creates the number of partitions based on the number of HDFS blocks. This leads to a large number of empty partitions which also get processed during piping. To remove this overhead, I want to filter out all the empty partitions from the RDD. I am aware of coalesce and repartition, but there is no guarantee that all the empty partitions will be removed.

Is there any other way to go about this?

回答1:

There isn't an easy way to simply delete the empty partitions from a RDD.

coalesce doesn't guarantee that the empty partitions will be deleted. If you have a RDD with 40 blank partitions and 10 partitions with data, there will still be empty partitions after rdd.coalesce(45).

The repartition method splits the data evenly over all the partitions, so there won't be any empty partitions. If you have a RDD with 50 blank partitions and 10 partitions with data and run rdd.repartition(20), the data will be evenly split across the 20 partitions.