Column Propagation

Push a column rename, type change, or removal from one workflow step downstream through every step that consumes it.

Description

When you change a column at the source — rename it, change its type, or remove it — every downstream step that maps to that column has to be updated to match. Column Propagation does that work for you in one confirmation.

Propagation is available from any step that has a ColumnMapper (Project Table, Calculate, Append, Merge, etc.). Two buttons in the mapper toolbar drive it:

  • Propagate All — propagate every column in the mapper
  • Propagate Selected — propagate only the columns you have selected in the mapper grid

Propagate a Column Change

  1. Open the workflow step containing the column you want to change
  2. In the ColumnMapper, make the change (rename, retype, etc.)
  3. Click Propagate All (or select rows and click Propagate Selected) in the mapper toolbar
  4. The Propagate Downstream dialog opens with a tree of every step that depends on the source step
  5. Tick the steps you want to apply the change to — child steps cascade automatically
  6. For aggregation steps, pick the aggregation function for any new columns in the lower Aggregation panel
  7. Click Confirm

The dialog defaults safely: when a downstream row has no explicit mapping for the column, the source name is reused as the target so no information is lost on the way through.

What Propagates

  • Column rename — source → target name change
  • Type change — dtype updated wherever the column appears
  • New columns added in this step — flow forward into downstream mappers
  • Strip operations applied to the source

Steps that don't reference the column are still shown in the tree but are unticked by default.

Errors and Retries

If a downstream step has been edited by someone else since the dialog was opened, the propagation will fail with a stale-version error. The dialog refetches the dependency graph automatically and lets you retry without losing your selections. If the refetch itself fails, your selections are still preserved so you can resolve the underlying issue and try again.