Push-downs, also known as query pushdowns, are a technique where transformation logic is pushed to the source database. This approach minimizes the need to store data physically and reduces the data transfer load over the network.
Typically, in a setup involving a Semantic Layer or data virtualization, the transformation logic is translated into SQL queries. These queries are then sent to the database. The source database executes these SQL queries to process the transformations efficiently.
This method, known as pushdown optimization, is particularly beneficial in enhancing mapping performance. It proves most effective when the source database is more adept at processing the transformation logic than the semantic layer itself, leading to faster and more efficient data handling.