Peek stage: Mapping tab
For the Peek stage, the Mapping tab allows you to specify how the output columns are derived, that is, what input columns map onto them or how they are generated.
The left pane shows the columns being peeked. These are read only and cannot be modified on this tab.
The right pane shows the output columns for each link. This has a Derivations field where you can specify how the column is derived. You can fill it in by dragging input columns over, or by using the Auto-match facility.