Power BI adds calculated columns to Direct Lake tables
The April 2026 update introduces calculated columns on OneLake tables in Direct Lake mode. Users can now define columns using functions such as UserPrincipalName without importing full datasets. DAX user-defined functions also received enhancements. Both features are currently in preview and require specific table configurations. The changes apply only to Microsoft Fabric environments with properly set up lakehouse tables.
Until now Direct Lake delivered speed only if you avoided calculated columns and stuck to simple measures. Most analysts therefore kept complex logic in imported tables or Power Query steps, accepting slower refreshes. The update removes that trade-off. Teams that already maintain clean lakehouse tables can add business logic directly in the model without losing the fast refresh. Teams still working from 15 Excel files and undocumented queries gain nothing until they first fix their data foundation.
Analysis
Ignore the preview announcement. Open your slowest inherited report, identify which tables can move to a lakehouse, and rebuild only the core fact table and two measures using the new user-context functions.
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