Direct Lake Fallback to DirectQuery with Row-Level Security

DP-600 By islever Editorial Last updated

Short answer

A Queries fall back to DirectQuery mode when the underlying Warehouse enforces row-level security (RLS).

Question

You have a Fabric tenant that contains a warehouse. The warehouse uses row-level security (RLS). You create a Direct Lake semantic model that uses the Delta tables and RLS of the warehouse. When users interact with a report built from the model, which mode will be used by the DAX queries?
  1. DirectQuery Correct Answer
  2. Dual
  3. Direct Lake
  4. Import

Key Takeaways

The exam tests the specific limitation of Direct Lake: while it supports RLS conceptually, the implementation requires querying the SQL endpoint, which forces a fallback to DirectQuery mode.

This question tests the behavior of Direct Lake semantic models when row-level security (RLS) is enforced on the underlying Warehouse. It establishes that RLS triggers a fallback to DirectQuery mode for DAX queries.

Common mistake: Many candidates select 'Direct Lake' because they know the model type and assume RLS is fully supported in that mode without performance or architectural penalties, ignoring the mandatory fallback mechanism.

Expert Analysis

Why the Answer Is Correct

When a Direct Lake semantic model connects to a table in a Fabric Warehouse that enforces Row-Level Security (RLS), the system cannot apply RLS directly against the parquet files in the lakehouse architecture. Instead, it must query the SQL analytics endpoint to evaluate the security rules. This process forces the DAX queries to fall back to DirectQuery mode. As noted by user wojciech_wie, "Row-level security only applies to queries on a Warehouse... Power BI queries... will fall back to Direct Query mode."

Why the Other Options Are Wrong

Import is incorrect because the model is explicitly defined as a Direct Lake semantic model, which does not use Import mode storage. Direct Lake is incorrect because, although the model is named Direct Lake, the presence of RLS on the Warehouse source disables the actual Direct Lake execution path for those queries, reverting them to DirectQuery. Dual is incorrect as it is not a standard mode for this specific Fabric warehouse scenario.

Community Comment Notes

Several users correctly identified the fallback behavior. User Jons123son initially argued for Direct Lake but cited documentation supporting RLS; however, other users like Markl and semauni clarified that the enforcement of RLS specifically triggers the fallback. User Wojciech Wie provided the most precise explanation, noting that RLS application necessitates the SQL endpoint query, thus causing the DirectQuery fallback. User XiltroX correctly dismissed Import as irrelevant.

Official Reference

https://learn.microsoft.com/en-us/power-bi/enterprise/directlake-overview

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always check for exceptions to the primary feature name. If a model is 'Direct Lake' but the source has constraints like RLS or certain view types, look for 'Fallback to DirectQuery' as the answer rather than assuming the mode name implies the execution behavior.

Frequently Asked Questions

Does Direct Lake support RLS?

Yes, but not natively against parquet files. It supports RLS by falling back to DirectQuery mode to query the SQL endpoint.

What causes Direct Lake to fallback?

Connecting to tables/views in the SQL analytics endpoint that enforce RLS or contain T-SQL views triggers a fallback to DirectQuery.

More DP-600 FAQ →

Community Votes

A
51%
C
49%

51% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 39 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 30 of 39

  1. wojciech_wie 👍 69
    A. Direct Query "Row-level security only applies to queries on a Warehouse or SQL analytics endpoint in Fabric. Power BI queries on a warehouse in Direct Lake mode will fall back to Direct Query mode to abide by row-level security." https://learn.microsoft.com/en-us/fabric/data-warehouse/row-level-security
  2. Estratech 👍 25 Answered C
    Direct lake . When users interact with a report built from a Direct Lake semantic model that uses Delta tables and RLS of the warehouse, the DAX queries will operate in Direct Lake mode. This mode is specifically designed for analyzing large data volumes in Power BI and is based on loading parquet-formatted files directly from a data lake without querying a Lakehouse or Warehouse endpoint. Unlike DirectQuery, there is no translation from DAX to other query languages, and it does not execute queries on other database systems. This results in performance similar to import mode, with the added benefit of picking up any changes at the data source as they occur12. Direct Lake mode supports row-level security (RLS), ensuring that users only see the data they have permission to view. It combines the advantages of both DirectQuery and import modes while avoiding their disadvantages, making it an ideal choice for very large models and models with frequent updates at the data source2.
  3. Jons123son 👍 6 Answered C
    C. https://learn.microsoft.com/en-us/fabric/get-started/direct-lake-overview "Before using Direct Lake, you must provision a lakehouse (or a warehouse) with one or more Delta tables in a workspace...Direct Lake also supports row-level security and object-level security so users" And it is Fabric exam, so the obvious correct answers is a Fabric feature.
  4. IshtarSQL 👍 5 Answered A
    When users interact with a report built from a Direct Lake semantic model, which leverages row-level security (RLS) and Delta tables from a warehouse, the DAX queries will operate in DirectQuery mode.
  5. IshtarSQL 👍 4
    Known issues and limitations Currently, Direct Lake models can only contain tables and views from a single Lakehouse or Data Warehouse. However, tables in the model based on T-SQL-based views cannot be queried in Direct Lake mode. DAX queries that use these model tables fall back to DirectQuery mode. https://learn.microsoft.com/en-us/power-bi/enterprise/directlake-overview
Show 25 more comments
  1. DilaniI 👍 4
    Both DirectQuery and DirectLake support RLS.The key word here is that tenant already had a Semantic Warehouse built.To query that one you need to use DirectQuery.Therefore the answer is A.But for the real user they can use DirectLake as well hear sinc eboth of them support RLS.Answer is A for this question.Thank you.
  2. semauni 👍 3 Answered A
    "When a Direct Lake semantic model table connects to a table in the SQL analytics endpoint that enforces row-level security (RLS), queries that involve that model table will always fall back to DirectQuery mode. Query performance might be slower." The question asks specifically about RLS, so you might already guess that this is a special situation. Always a good idea to look it up in the Fabric documentation if you've never seen this specific case. Reference: https://learn.microsoft.com/en-us/fabric/get-started/direct-lake-overview
  3. Markl 👍 3 Answered A
    A query always falls back when the semantic model queries a view in the SQL analytics endpoint, or a table in the SQL analytics endpoint that enforces row-level security (RLS).
  4. Shivam_1122 👍 3 Answered A
    Written in docs itself https://learn.microsoft.com/en-us/fabric/get-started/direct-lake-overview it will fallback to DQ
  5. XiltroX 👍 3 Answered A
    What the heck is "Import" in DAX? Its DirectQuery only.
  6. nappi1 👍 2 Answered C
    In the scenario, when users interact with a report built from a Direct Lake semantic model that utilizes Delta tables and row-level security (RLS), the DAX queries will primarily operate in Direct Lake mode. So, the correct answer is C. Direct Lake This mode is designed to provide optimal performance for DAX queries, allowing them to read data directly from the Delta tables. However, if there are any limitations or memory pressures, the model may fall back to DirectQuery mode. But under normal circumstances, you can expect the queries to run in Direct Lake mode, leveraging the benefits of RLS effectively
  7. Charley92 👍 2 Answered C
    When a Direct Lake semantic model is created and used, the DAX queries interact directly with the data in OneLake without importing it into memory (as in Import mode) or querying it from a remote data source (as in DirectQuery mode). The key features of Direct Lake mode include: Direct access to Delta tables stored in OneLake. Low latency querying without requiring data to be loaded into memory first. Integration with features like Row-Level Security (RLS) when configured in the underlying warehouse.
  8. aks2304 👍 2 Answered A
    The correct answer is A. DirectQuery. When users interact with a report built from a Direct Lake semantic model that uses Delta tables and row-level security (RLS), the DAX queries are executed in DirectQuery mode. This is because RLS requires the queries to be evaluated at the source to enforce security rules dynamically, and Direct Lake does not currently support RLS natively. Therefore, the system falls back to DirectQuery mode to ensure RLS is applied correctly.
  9. Nefirs 👍 2 Answered A
    A if the semantic model has direct lake connection to the source, then the report connecting to this semantic model has direct query.
  10. orallony 👍 2 Answered A
    IT will fall back to direct query since the RLS is configure on the Data source and not in the semantic model
  11. b65ecca 👍 2 Answered A
    Because it says "RLS of the warehouse" I'd be more likely to go for DirectQuery than Direct Lake
  12. c58ebda 👍 2
    A. https://fabric.guru/power-bi-direct-lake-mode-frequently-asked-questions
  13. Huepig 👍 2 Answered A
    RLS on the warehouse will fail back to direct query
  14. Red_lotus85 👍 2 Answered A
    A! Read the limitation of direct lake
  15. Momoanwar 👍 2 Answered A
    Dax and fallback its direct query
  16. jcu614 👍 1
    C. Direct Lake mode is a specific feature of Microsoft Fabric that allows Power BI to directly access Delta tables in a Fabric Lakehouse or Warehouse without needing to import data into Power BI or rely on DirectQuery alone. This mode enables real-time interaction with the data stored in the lake without additional overhead. DirectQuery would be more relevant if the data were in a database that supported DirectQuery rather than Delta tables in Fabric's Lakehouse/Warehouse.
  17. wudixh 👍 1 Answered C
    Answer from Microsoft Copilot: C. When users interact with a report built from a Direct Lake semantic model that uses Delta tables and RLS, the DAX queries will use Direct Lake mode (Option C) by default. This mode allows the semantic model to read Delta tables directly from OneLake. However, if there are certain conditions like memory pressure or unsupported features at the data source, the model might fall back to DirectQuery mode
  18. 282b85d 👍 1 Answered C
    Direct Lake mode is a new feature in Power BI that allows direct querying of Delta tables in a data lake without the need to import data into the Power BI model. This mode "combines" the advantages of DirectQuery and Import modes, providing real-time access to data while leveraging the performance benefits of in-memory caching for certain queries.
  19. David_Webb 👍 1 Answered A
    While Direct Lake mode doesn't query the SQL endpoint when loading data directly from OneLake, it's required when a Direct Lake model must seamlessly fall back to DirectQuery mode, such as when the data source uses specific features like advanced security or views that can't be read through Direct Lake.
  20. Beejay69 👍 1 Answered D
    D. https://learn.microsoft.com/en-us/fabric/get-started/direct-lake-overview On the other hand, with import mode, performance can be better because the data is cached and optimized for DAX and MDX report queries without having to translate and pass SQL or other types of queries to the data source.
  21. LeeAspiring 👍 1
    A. Direct lake - Row-level security only applies to queries on a Warehouse or SQL analytics endpoint in Fabric. Power BI queries on a warehouse in Direct Lake mode will fall back to Direct Query mode to abide by row-level security.
  22. a_51 👍 1 Answered A
    A as has been shared before https://learn.microsoft.com/en-us/fabric/data-warehouse/row-level-security
  23. SharkyShark 👍 1
    Its A. Based on https://learn.microsoft.com/en-us/fabric/data-warehouse/row-level-security
  24. ba2bfdf 👍 1 Answered A
    https://learn.microsoft.com/en-us/fabric/get-started/direct-lake-overview
  25. semauni 👍 1
    I wanted to make a voting comment, so please remove this one :)

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