When you configure pushdown optimization for a session with pass-through partitioning, the database processes data without redistributing rows among partitions. All rows in a single partition stay in the partition after crossing a pass-through partition point.
You must configure all partition points for pass-through partitioning to push all transformation logic to the database. For example, a session has four partition points. You configure the first three partition points for pass-through partitioning and the last partition point for hash auto-keys partitioning. The Integration Service pushes all transformation logic to the database, except the transformations at and after the last partition point. The Integration Service processes the transformations at and after the last partition point.