I have a workbench which takes two schemas, merges them using a FeatureMerger, takes the output from that and merges it with a third dataset schema. This is then fed into a SchemaMapper transformer, with:
- Source attribute -> Destination attribute mapping
- Source attribute -> Filter attribute value filter
- New attribute = New attribute value
However, the output, when viewed with an inspector and when written to a GDB feature class, is identical to the input, albeit with the _schemamapper_row_ids attribute added (and appearing to be populated with data indicating the mapping has worked. My understanding is at the very least, the new attributes should be appearing to indicate the transformer is behaving as expected.