Power BI Filter Context - adding a measure to matrix then ignores all relationships
I have a very simple data model with one relationship, and it works as expected (on the left). However, when I add a measure that's always valid (in this case, something that displays today's date), the visuals I have ignore the relationships in my model and display all combinations of values, even if they're not valid or matching in the data model.
What's going on here? I would expect that the measure, which has no filter context of its own, would be run for each row and just display today's date. What seems to be happening, though, is that it's being evaluated for every single combination of values, even when the relationship should already be excluding those.
A measure isn't really associated with a table so the relationships and filters only apply to them insofar as the measure involves tables and columns. This is useful in cases where you want to write a measure that involves unrelated tables since otherwise those wouldn't be possible.
Since your date measure doesn't involve any tables, it's not constrained by their relationship. You can force it to be though. For example,
Today Date = IF ( NOT ( ISEMPTY ( Ones ) ), TODAY () )
or more implicitly with something like this
Today Date = MAXX ( Ones, TODAY () )