Formula.Firewall In Power Query

Chris Webb explains when you might get a Formula.Firewall error in Power BI or Power Query:

The important difference here is that there is now one step in this query instead of two: the query and the filtering take place in the same step. Even more importantly, regardless of the data privacy settings, the query fails with the error:

Formula.Firewall: Query ‘DimDate With Native Query Single Step Fails’ (step ‘Source’) references other queries or steps, so it may not directly access a data source. Please rebuild this data combination.

The problem here is that the Power Query engine is not allowed to access two different data sources originating from different queries in the same step – as far as I understand it this is because it makes it too hard for the engine to work out whether a step connects to a data source or not, and so which data privacy rules should be applied.

This is an interesting downside to putting in complex data privacy rules.

Related Posts

Reading SQL Server Error Logs

Thomas Rushton has a script for us: Why Script This? What’s Wrong With SSMS’s GUI?Well, although SSMS does allow you to look at the error logs, it’s not very helpful for filtering – you can only filter for items that match, rather than exclude items. There are a few other filters as well – I […]

Read More

Power Query and the Benefits of Immutability

Chris Webb explains why immutable expressions can be faster to run multiple times than mutable processes: Instead of taking the value #”Sorted Rows”[Column2]{0} and storing it in the variable Column2 then adding Column2 four times, I’m  adding the expression #”Sorted Rows”[Column2]{0} together four times. The query returns the same number as the previous query. However […]

Read More

Categories

June 2017
MTWTFSS
« May Jul »
 1234
567891011
12131415161718
19202122232425
2627282930