The Data Integration Service might remove a Filter transformation if the filter condition evaluates to FALSE for the data rows. For example, a mapping has two Filter transformations that filter data from two relational sources. A Filter transformation has the filter condition Country=US, and the other Filter transformation has the filter condition Country=Canada. A Union transformation joins the two relational sources and has the filter condition Country=US. The Data Integration Service might remove the Filter transformation with the filter condition Country=Canada from the mapping.

The Developer tool enables the branch pruning optimization method by default when you choose the normal or full optimizer level. You can disable branch pruning if the optimization does not increase performance by setting the optimizer level to minimal or none.