I think I found the root cause of this different behavior. Forget about the ampersand in the parent.
It is just collapsed/expanded status of [c] in the dimension that impacts the different behavior of TM1FILTERBYPATTERN function.
In multiple rollups for [c] in the dimension, TM1FILTERBYPATTERN function just look up for the first appearance of the [c], if that [c] is expanded, then TM1DRILLDOWNMEMBER function can show the expanded status as well. if it is collapsed, then collapsed also.
See the difference below,
0. The whole structure now,
- 111.PNG (3.15 KiB) Viewed 9652 times
1. After show all, the first [c] in [ba] is collapsed and the second [c] is expanded.
- 222.PNG (5.86 KiB) Viewed 9652 times
- 333.PNG (10.03 KiB) Viewed 9652 times