[Spark Streaming]: Why planInputPartitions is called multiple times for each micro-batch in Spark 3?

Hi All While upgrading our custom streaming data source from Spark 2.4.5 to Spark 3.2.1, we observed that the planInputPartitions() method in MicroBatchStream is being called multiple times(4 in our case) for each micro-batch in Spark 3. The Apache Spark documentation also says that : The

Why planInputPartitions is called multiple times in a micro-batch?

Hi, I'm developing a new Spark connector using data source v2 API (spark 3.1.1). I noticed that the planInputPartitions method (in MicroBatchStream) is called twice every micro-batch. What the motivation/reason is? Thanks, Kineret