Category: Performance Tuning

James Serra has updated a guide on Power BI performance optimizations:

This post is a complete replacement for and update to my April 2022 post, Power BI Performance Features. That post focused on several performance features that were new or in preview at the time. Four years later, many of those features have matured, Microsoft Fabric has changed the architecture choices available to us, and Direct Lake has become an important part of the conversation. So rather than keep adding notes to an old feature list, I decided to step back and answer the more useful question: How should you design, diagnose, and improve Power BI performance today?

Here’s the bottom line: Power BI performance is not one feature, one setting, or one capacity size. It is the result of a chain that includes the data source, data preparation, storage mode, semantic model, DAX, report design, security, refresh process, and Fabric capacity. A weakness anywhere in that chain can become the bottleneck, which is why randomly changing DAX or buying more capacity often does not solve the real problem. The best approach is to make the right architectural choices first, measure what is slow, and then fix the layer that is actually causing the delay. For more info, see Optimization guide for Power BI.

Click through for James’s guidance.

Andy Brownsword explains one performance improvement technique for Power BI data transformations:

As a database developer, when I started using Power BI, I was concerned about it retrieving reams of data only to perform transformations downstream. The Power Query editor misleads us into thinking the retrieval and transformations are applied sequentially.

Thanks to Query Folding, that’s not usually the case. And that gives us more power to extract performance from the database.

This only works in situations where there’s something downstream to perform that processing, like a relational database. And one of the areas where you can affect performance, either positively or negatively, is in organizing operations such that you have a stretch of foldable operations. That way, all of it can run as one operation in the database.