Filter ActiveAdmin with Postgresql json column on specific json keys

I have a Deal model that features a json column called deal_info. It's actually an array of JSONs.

I'm using active admin.

For example :

deal1.deal_info = [ { "modal_id": "4", "text1":"lorem" }, 
          { "modal_id": "6", "video2":"yonak" },
          { "modal_id": "9", "video2":"boom" } ] 
deal2.deal_info = [ { "modal_id": "10", "text1":"lorem" }, 
          { "modal_id": "11", "video2":"yonak" },
          { "modal_id": "11", "image4":"boom" } ]

As first step now I would like to have a filter that would enable me to filter the deals based on the fact that deal_info json column includes at least one time the modal_id in one of its included json.

It would enable me in a select dropdown to choose for example modal_id = 6 and would filter the list of Deals to only show deal 1 (see example above).

One of the further challenge is that I need to be able to remove duplicates on the select dropdown in order not to have multiple times the same id: here for example i can't have select = [4,6,9,10,11,11]...each modal_id can only appear once.

I only found this but it did not work for me.

My current Active Admin Code

ActiveAdmin.register Deal do
  filter :modal_id,
  as: :select 
  collection: deal_info.all.to_a.map ???? 
end