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Microsoft

DP-500 · Question #46

You are optimizing a dataflow in a Power BI Premium capacity. The dataflow performs multiple joins. You need to reduce the load time of the dataflow. Which two actions should you perform? Each…

The correct answer is C. Execute foldable operations before non-foldable operations. E. Place the ingestion operations and transformation operations in separate dataflows. To reduce Power BI dataflow load times, prioritize foldable operations to leverage source system processing and separate ingestion from transformation into distinct dataflows for better resource management.

Query and transform data

Question

You are optimizing a dataflow in a Power BI Premium capacity. The dataflow performs multiple joins. You need to reduce the load time of the dataflow. Which two actions should you perform? Each correct answer presents part of the solution. NOTE: Each correct selection is worth one point.

Options

  • AReduce the memory assigned to the dataflows.
  • BExecute non-foldable operations before foldable operations.
  • CExecute foldable operations before non-foldable operations.
  • DPlace the ingestion operations and transformation operations in a single dataflow.
  • EPlace the ingestion operations and transformation operations in separate dataflows.

How the community answered

(40 responses)
  • A
    13% (5)
  • B
    5% (2)
  • C
    80% (32)
  • D
    3% (1)

Why each option

To reduce Power BI dataflow load times, prioritize foldable operations to leverage source system processing and separate ingestion from transformation into distinct dataflows for better resource management.

AReduce the memory assigned to the dataflows.

Reducing memory assigned to dataflows would likely degrade performance, not improve it, especially for dataflows performing multiple joins which are memory intensive.

BExecute non-foldable operations before foldable operations.

Executing non-foldable operations before foldable operations prevents query folding, forcing Power BI to process more data locally and increasing load times.

CExecute foldable operations before non-foldable operations.Correct

Executing foldable operations before non-foldable ones allows the Power Query engine to push transformations back to the source system, reducing the amount of data transferred and processed in Power BI. This concept, known as query folding, significantly improves performance by offloading work to more powerful source databases.

DPlace the ingestion operations and transformation operations in a single dataflow.

Placing all operations in a single dataflow can lead to complex, harder-to-manage dataflows and prevent the optimization benefits of separate staging and transformation layers.

EPlace the ingestion operations and transformation operations in separate dataflows.Correct

Placing ingestion and transformation operations in separate dataflows (staging and transform dataflows) allows for better modularity, reusability of ingested data, and improved refresh performance. Staging dataflows can load data once, and multiple transformation dataflows can reference this data without re-ingesting it, reducing overall load on the source and Power BI capacity.

Concept tested: Power BI dataflow optimization, query folding, dataflow architecture

Source: https://learn.microsoft.com/en-us/power-query/queryfolding

Topics

#Dataflow optimization#Query folding#Power BI Premium#Dataflow architecture

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