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DAX Memory Usage from Filtering on a Table

Chris Webb talks Power BI anti-patterns:

Following on from my last post on the Query Memory Limit in Power BI, in this post I want to look at one of the most common DAX antipatterns and its effect on query memory usage: filtering on a whole table, rather than an individual column, in the filter parameters of the Calculate() function. A lot has already been written on this particular antipattern from the point of view of query performance – for example see here and here – but it’s only with the recent addition of the Execution Metrics Profiler/Log Analytics event that you can see how bad it is for memory usage too.

Read on for an example. In Chris’s case, there’s a 3x memory difference between doing the right thing and the wrong thing, so this can easily add up.

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