Dynamic RLS and LOOKUPVALUE vs Many to Many Join

Hi user131313 ,

Thank you for reaching out to Microsoft Fabric Community Forum.

Below are  key points to help guide your decision :

1)LOOKUPVALUE() can slow down on large fact tables, especially in calculated columns.
2)LOOKUPVALUE Can cause performance issues on large datasets (especially in calculated columns)
3)Many to Many relationships can be faster, but only if the bridge table and related logic are clean and non-redundant.
4)In large models, prefer using measures instead of calculated columns, and test using Performance Analyzer.
5)Since you’ve already found a M:M solution that avoids LOOKUPVALUE():
6)Go with the Many to Many approach if It aligns with your data model structure.
7)Use LOOKUPVALUE() if the relationships aren’t easily modelled.

8)test both approaches using DAX Studio or the Performance Analyzer in Power BI to see what works best in your scenario.

Regards,

Chaithanya.