Pushdown optimization is a concept using which you can push the transformation logic on the source or target database side. When you have a source as the database table, you can make use of a SQL override to remove the logic written in the transformation. When you use the SQL override, the session performance is enhanced, as processing the data at a database level is faster compared to processing the data in Informatica. You cannot remove all the transformations from the mapping. The part of transformation logic that can be pushed at the source or target level is referred to as pushdown optimization.

Consider that you have a mapping with a sequence indicated as follows:

Source - Source Qualifier - Filter - Sorter - Aggregator - Expression - Lookup - Rank - Target.

In Filter transformations, we are filtering the data in a particular location. In Sorter transformations, the data is sorted in a particular department ID. In the Aggregator, we are grouping the data in the department...