Sort by field which containing "unique id's" is not possible?

Hello Bubblers,

Another question from a rookie. I have a Thing which has a field “Impressions”. This field is not a number, but a list of Users (unique id’s) that have “seen” this Thing.

I am trying to output a list of Things sorted by the number of Impressions. Should be easy… However, Bubble doesn’t allow me to sort on a this field (presumably because it contains unique id’s of a different Thing).

A possible solution I could think of would be to add another field “Impressions_Count” and increment it whenever a User is added to “Impressions”. But this is somewhat really strange to create a second DB field for the same purpose. Why can’t I sort? Any text field allows me to output the Impressions:count!