How to filter collection fields in Cards?

I tried to use filter the collectrion fields in board cards, but only can find the select dropdown ‘suggested’ entities filter, which does not filter existing related entities. For example:


The representation of a collection field on a card is not a fully-functional relation field view - you can’t add filters (or colour coding, or sorting)

We’ve created formulas to filter properly. But be aware of creating too much formulas since it can slow down the workspace.

If there were to be filters on collections on cards, this would require a ‘front-end’ filter setting since it would be a function of the view. This could potentially cause a performance hit, since it implies that the view needs to not only query/filter the entities which are to be shown, but also query/filter the entities linked to the entities.
This has the potential to scale quite badly.

i.e. “show me the projects (filtered by this and that) and then for each of them, show me the linked tasks (filtered by this and that)”
If you have 50 projects, and each has on averaged 20 tasks, this requires querying/filtering 1000 entities before the board view can be rendered.
If a project is linked to 5 assignees on average, this requires an additional 250 queries.

At the moment, the filters which are available for collections on entity view relations are limited to those items linked to the (single) entity being viewed. So for the above example relations, the query is limited to 20 tasks + 5 users (on average).

Overall, it’s this extra dimension that means that a performant implementation is not that technically easy to do.