When setting up the filter widget on a layer hosted in my organization's spatiotemporal big data store, I noticed that the drop down you typically get when you set it to ask for the user to enter a unique value. Typically, this setting will generate a list of unique values that exist in in the field you are trying to filter, but for a STBDS layer, it just does nothing or spins a loading circle.
I submitted a support case, and they said that it does not work because aggregated queries are not currently supported for the SBDS.
![Web AppBuilder filter widget configured on a STDBS layer to ask the user for unique value from drop down, but the drop down is not generating.](/legacyfs/online/495582_ArcGIS Ideas Submittal.JPG)