Support for Heterogenous tuples with :db/tupleTypes supporting :db.type/refs

[arkRedM]

In datomic there is a way to combine data as

{:db/ident :x/y  
 :db/valueType :db.type/tuple
 :db/tupleTypes [:db.type/ref :db.type/string], 
 :db/cardinality :db.cardinality/one}` (or many).

I understand the types are more friendly in js but is there a way to support ref resolution?
hacking around for this will make code less clean.

[tonsky]

Interesting! I haven’t thought about it. Yes this makes sense, thank you!

[zeitstein]

Would be interested in this exact use case: storing a tuple [:db.type/ref :db.type/string]. Ideally, it would be :db.cardinality/many – hence, storing multiple tuples per attribute. Any plans to support this?

[tonsky]

I wouldn’t mind it. Care to provide a PR?

[zeitstein]

Hey, I'm back to thinking about this. I'm no longer sure tuples are the best approach, so I would appreciate if you could provide some clarity.

My use case can be described in Clojure data as

{ ...
 :attr [{:ref1 -1, :ref2 -2, :val "string 1"} {:ref1 -3, :ref2 nil, :val "string 2"} ...]
 ...
}

My queries would target all combinations, e.g. querying for entities matching ref2 value, or both ref1 and val, etc.

Currently I use an intermediary entity, e.g:

:attr {:db/cardinality :db.cardinality/many, :db/valueType :db.type/ref, :db/isComponent true}

{:inter/ref1 -1, :inter/ref2 -2, :inter/val "string 1", :inter/order 0}

Which has the obvious downside of polluting indexes, but is nicely used in queries.

Alternative would be to store many 4-tuples [ref1 ref2 val order] on :attr. (So its heterogenous, not composite.) Given my query requirements above, would you say it would be worth pursuing the tuple idea (and the PR)? Thanks!

[tonsky]

Well it’s either all possible tuples or hash-join using queries. I’d probably prefer tuples

[seepel]

I'd love to take a crack at this feature. Do you have any guidance as to how you would go about it, and/or any tips on understanding and navigating the code base?

[tonsky]

@seepel that would be fantastic! I don’t have many tips, but I’d probably start by listing all the places where having refs in tuples would make a difference (transact, query, pull, entity), then writing tests for each and finally finding the best place to implement the logic. Happy to accept partial PRs!

[seepel]

That sounds like some solid advice, thank you!

I’ll admit, I started by greping for tupleAttrs and found myself a bit overwhelmed 😅