FetchXml powers turned out to be limited, and I’ve just discovered it the hard way

Actually, this is not how I discovered it. I was writing an SSRS report and the number of linked entities in my FetchXml query kept growing, so at some point the reports has stopped working:

That error message made me try my Fetch in the XrmToolBox, which lead to the error above, which, in turn, made me look at the documentation again… and there it is:

https://docs.microsoft.com/en-us/powerapps/developer/common-data-service/use-fetchxml-construct-query

It seems the limitation has been there forever, but it’s only been added to the docs recently:

So I’ll probably have to make the report work somehow else. Might have to start using subreports instead of bringing all the data through fetch…