DAX Performance Optimization with NOT and COUNTROWS
Note: This question is part of a series of questions that present the same scenario. Each question in the series contains a unique solution that might meet the stated goals. Some question sets might have more than one correct solution, while others might not have a correct solution. After you answer a question in this section, you will NOT be able to return to it. As a result, these questions will not appear in the review screen. You have a Fabric tenant that contains a semantic model named Model1. You discover that the following query performs slowly against Model1. You need to reduce the execution time of the query. Solution: You replace line 4 by using the following code: NOT ( CALCULATE ( COUNTROWS ( 'Order Item' ) ) < 0) Does this meet the goal? - 
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Replacing a DAX filter with a logically equivalent expression using NOT and COUNTROWS does not reduce execution time because the underlying calculation is still evaluated.
Replacing a DAX condition with a logically equivalent expression using NOT and COUNTROWS does not improve query performance. This page confirms that logically equivalent DAX formulations yield the same execution time.
Choosing Yes because the DAX syntax looks different, assuming it triggers a different query plan without verifying logical equivalence.
Community Discussion (3 comments)
Comments & Corrections
No comments yet — spotted an error or have a note? Share it below.
Expert Analysis
Why the Answer Is Correct
The correct answer is No because the proposed solution replaces the original DAX expression with one that is logically equivalent. Since both expressions must evaluate the sameCALCULATE and COUNTROWS operations against the 'Order Item' table, the VertiPaq engine processes the same amount of data and performs the same calculations, resulting in identical execution times.Why the Other Options Are Wrong
Choosing Yes would incorrectly imply that simply rearranging a DAX condition into a NOT statement inherently optimizes the query. Performance optimization requires reducing the computational workload—such as filtering earlier or using a more efficient function—not just altering the logical syntax without reducing the work.Community Comment Notes
Community members agree that the change is logically equivalent and thus offers no performance benefit, as Pegooli noted: "This change is logically equivalent to the original condition". Martin_Nbg also pointed out that "Performance would be about the same", reinforcing that syntax shifts without computational reduction do not optimize DAX.Official Reference
Exam Strategy
When evaluating DAX optimization solutions, check if the proposed change actually reduces the data scanned or the complexity of the calculation. Logically equivalent expressions will not improve performance.
Related Analysis
Practice All DP-600 Questions
Access 115 questions with complete answers and detailed explanations.
View Full DP-600 Practice Test →