Prevent Warehouse Queries from Referencing Lakehou...

Hi Fabric Team,

I’m writing to report a critical issue we've encountered while using Microsoft Fabric for our ETL and ELT workloads. We rely heavily on both Warehouse and Lakehouse components.

As expected, when configuring a copy activity, we can use SQL queries if the source is a Warehouse. However, we discovered that Fabric currently does not prevent queries from referencing Lakehouse tables in a Warehouse-scoped query.

This unexpected behavior led to a serious issue in one of our production pipelines—records from a daily load were not copied to Oracle as expected. After an in-depth investigation, we traced the problem to a query that mistakenly referenced a Lakehouse table, even though the copy activity source was configured as a Warehouse. Fabric did not flag this mismatch, and the copy activity silently failed to extract the intended data.

This kind of inconsistency is very hard to detect and can have severe consequences in production environments.

🛠️ Suggested Improvement:
Implement a validation step during query submission in copy activities to ensure that all referenced tables belong to the selected source type (i.e., Warehouse). This would prevent these subtle but impactful issues.

Thank you for your attention to this matter.

Kind regards,
Yazdan Aghajanian
Data Engineer