The Joiner transformation master source must have significantly fewer rows than the detail source.

The detail source must be large enough to justify the optimization. When the Data Integration Service applies semi-join optimization, the method adds some overhead time to mapping processing. If the detail source is small, the time required to apply the semi-join method might exceed the time required to process all rows in the detail source.

The Data Integration Service must be able to obtain source row count statistics for a Joiner transformation in order to accurately compare the time requirements of the regular join operation against the semi-join operation.