Why doesn't ALL function ignore filter when data is sliced by columns in pivot table?

Question

I'm new to the DAX world and I just faced a conceptual misunderstanding.

While I was trying to debug a measure, I found a unexpected (for me) behaviour with the ALL function. I wrote a simple measure COUNTROWS(ALL(Table)) but to my surprise, when I sliced the data by a column, the same number did not appear in each cell in the values field, ignoring the filter context in the way I was expecting:

So, what am I missing?

Answer 1

Since there are no BUYs on e.g. 01/08/2017, it's not even evaluating the measure. Since that cell doesn't correspond to any rows in the original table, it's not doing any computations.

If you had a BUY and a SELL on the same day, it should show up in both columns on that day.