UPDATE: IT SEEMS THE BUG HAS NOW BEEN FIXED. THREE HOORAYS FOR THE POWER BI TEAM!
Recently I stumbled across a quite annoying error in the Power BI service. I uploaded two working reports from Power BI Desktop to the cloud service. Each report connects to its own cube and both cubes are in the same SSAS MD database. On the server, I have a gateway installed that connects this SSAS MD database to the online service.
Now, when I browse one of the reports, everything works fine. Once I open the other report, the visuals of this second report stop working:
This visual itself displays the error “This visual has unrecognized fields”. A bit odd, since everything worked just fine in Power BI Desktop. When clicking on the See details link, the following pop-up appears:
Apparently Power BI has trouble to identify some fields (in this case it’s the name of the measure group). What’s curious though, is that some fields of the second report still work. Those fields are attributes of the conformed dimensions. In other words, fields that are shared between the two cubes still work.
I monitored the queries to the SSAS MD database using Profiler: only the working queries came through. Queries from the non-working visuals didn’t even reach the cube. So this means they are stopped before the query is sent to the SSAS MD instance. I did a heavy investigation into the on-premise gateway. I reviewed all of the logs, but nothing spectacular came out. I reviewed all of the HTTPS traffic on the gateway server using Fiddler. With this tool I could retrieve the JSON that was sent between the gateway and the Power BI service. The JSON of the non-working visuals contained the following error message:
Could not resolve model references in the Semantic Query
The JSON also contained a help URL, but of course it doesn’t work. So for some reason Power BI (either the service or the gateway) can’t find the fields that are being referenced by the visual. However, the queries on the conformed dimensions are sent to the correct cube, so it’s not the case that Power BI is sending everything to one single cube and it ignores the other. Even more, after the weekend I tried again and suddenly the first cube stopped working but the second one worked without any issue. This led me to believe there was some weird caching issue going on.
I posted my findings on the Power BI forum and the Power BI team was quickly to confirm it’s a caching bug when working with multiple cubes in the same SSAS MD database. Apparently they didn’t test with the AdventureWorks cubes? They are currently working on a fix and I hope it’s released soon. I’ll update this blog once I know more.