Filter nested Data Grid by the value of one of its parent fields
I'm trying to filter a nested Data Grid by the value of one of its parents fields.
For example, I want to show a list of users, while each user element has a list of its friends.
As an input, I have a Data Master called Users, where (among other fields) I have a user ID and a Friends field, which contains comma-delimited list of this user's friends.
In order to accomplish that, I've created a Data Grid for this Data Master, and put another, nested Data Grid for the same Master inside the Grid Cell. Afterwards, I've tried to achieve the filtering of the nested Data grin on page load in the following ways:
1. FILTER(UsersDataMaster, (NestedFriendsField HAS ParentUserId)) - returns an empty data grid
2. FILTER (UsersDataMaster, (ParentFriendsFieldHAS NestedUserId)) - returns an empty data grid (the friends fields are built in the way that if one user have another one in friends, the another one has the first one in friends as well)
3. FILTER(UsersDataMaster, SELECT(UsersDataMaster, FriendsField) HAS ParentUserId) - returns all of the Data Master records (took this as a reference)
What do I miss?