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Finding DAX Dependencies

Chris Webb tries out a DMV:

If you’re monitoring activity in Power BI, for example using Log Analytics, you’ll know that you can capture the DAX queries generated by your published Power BI reports. How do you make sense of them though? You may want to know which tables, columns or measures are being used by a query – maybe so you can work out which ones aren’t being used and can be deleted. I always thought the only way to do this would be to parse the DAX query, which would be incredibly difficult to do. Yesterday, though, Igor Cotruta pointed out on Twitter that there’s a really easy way to do this that I didn’t know about, using the DISCOVER_CALC_DEPENDENCY DMV. I’ve used this DMV before and blogged about it here, but what was new to me is that you can pass a DAX query into the QUERY restriction (it is all documented here). To see how it works let’s look at a simple example.

This looks pretty cool.