What happens when data fields change or merge?

When data fields change or merge, segments that depend on those fields break. A segment rule that references a field called purchase_date will fail if that field is renamed last_purchase or combined with another attribute. Broken segments either return zero members or throw errors.

Before changing fields, audit all dependencies. Identify every segment, automation, and report that references the affected field. Most ESPs provide tools to search for field usage across campaigns and workflows.

Update segment rules to reference the new field structure before or immediately after migration. If timing gaps exist, pause dependent campaigns to avoid sending to empty or incorrect audiences.

Backfill historical data when possible. If the new field structure aggregates or transforms existing data, ensure past records are converted so segments reflect complete history rather than just post migration activity.

Communicate changes to everyone who manages segments or reports. Documentation prevents confusion and reduces the risk of someone rebuilding rules against deprecated fields.

Changing the map legend mid voyage confuses the entire crew. Update carefully and announce loudly.