I have two list fields in my Database: Tags and [Project Tags]. (Tags is an x:many relation and [Project Tags] is a lookup of an x:many field.) I want to combine them into a single list field [All Tags], so if (eg) Tags = (foo, bar) and [Project Tags] = (baz, bam) then [All Tags] = (foo, bar, baz, bam). Is this possible? I can’t figure out how to do it with a formula or a lookup. Extra complication: ultimately I actually want the unique set of all tags, so if (eg) Tags = (foo, bar) and [Project Tags] = (foo, baz) then [All Tags] = (foo, bar, baz). I can do the unique in a second formula if necessary/possible. Thanks!

[image] Matt_Blais: If a Formula field could return a collection, and we had functions for collection operations like merge/union and intersection, that would be very cool :smiley: I assume a collection would never contain multiple references to a single entity, so we wouldn’t need a “unique” function. Formulas can return collections, and collections never contain the same reference multiple times. I guess this means that merge is not applicable, and unique is implied.

Sorry: I guess bringing up Reduce() and Map() was a bit off-topic, but yes: Join() is a specific example of a Map() + Reduce(), where the entities are mapped to strings and then reduced with string concatenation. So if you exposed Map() and Reduce() functions to us directly then we could implement our own Join(), eg: as Reduce(Map([Tags], ToText), ‘+’) but we could also implement any (supported) Map() function or any supported Reduce() function, or any combination, which would be very powerful (as long as you support more than ToText() in Map(), and more than ‘+’ in Reduce()).

So I guess collections are sets, in which case yes they’ll be unique by definition, and you would just need to supply (off the top of my head) Union(), Intersect(), Diff() functions: and I guess also Complement() if the universe for that particular collection was finite and enumerated.

My gut feeling is that union is the most useful. I’m not sure how many users would need intersect, diff or complement. Perhaps community members will come up with use cases :slightly_smiling_face:

Yes, 100%. Union() would solve my immediate problem: I just figured if you’re going to add that then you might consider adding (at least) Intersect() and Diff() at the same time, because together those operations would enable a lot more use cases than Union() alone.

Can you provide some example use cases that need intersect or diff. It’s always interesting to hear what people want to achieve.

Thanks! What are References? I can’t find an explanation of them in the UI or docs; just lots of people commenting on how much they like them!

“References” would be links to entities in a Rich Text field. In an entity that has been linked, all the links to it are shown in a collection in the entity view: [image] Or possibly another name for Relation fields / collections?

Does this help? Bi-Directional Hypertext Links in Fibery How to use bi-directional links in Fibery to connect all the things.

Yes, thanks: I get it now: although I guess Reference isn’t surfaced as an official Collection in the Database (or any other) view of a referenced Database?

How to union two list fields in the same Database?

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Chr1sG February 4, 2022, 8:14am 30

See here for a backdoor API to programmatically access references

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How to union two list fields in the same Database?

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