Hey - glad you found the answer so quickly 🙂 but you're 100% right the tests are by far the best way to sanity check what's possible or not. And Datalog certainly has a learning curve...I spent most of last Saturday thinking about how to efficiently do the equivalent of a FULL OUTER JOIN in a single efficient Datalog without repeating a bunch of (or (not-join ... work. I've reluctantly had to give up thinking about it for now 😅

Thanks. For some reason, I’ll spend a bunch of time looking for something, decide I should just ask, then after asking, figure out a way to find the answer. I might need to order one of those rubber ducks after all... I might try my hand at some docs for the various Datalog operators with examples if you think it’d be helpful. edit: if only for learning purposes

Aha, we would never turn down an offer of writing docs! Another tutorial instalment to cover this area is also warranted.

Awesome to see Crux working already 🎉 We use it for all our BI needs in the company 🙂

Or, not-join and various rules will already execute as subqueries under the hood. There's no explicit concept of subquery though. What situations are you thinking about?

Also there's really no penalty when running multiple queries from Clojure if everything is in-process and you use open-db

I was running into issues with querying entities with multiple values for a key: {:crux.db/id :entity :dependencies {:dep-1 :dep2}} Let's say you want entities that only depend on :dep-1. This doesn't work: {:find [e] :where [[(== #{:dep-1} d)] [e :dependencies d] [e :dependencies d2] [(!= #{:dep2} d2)]]} And neither did a few others, always either returning entity when they shouldn't (like the below). Or returning nothing (like the above). {:find [e] :where [[(== #{:dep-1} d)] [e :dependencies d] (not-join [e] [e :dependencies d2] [(!= #{:dep-1} d2)])]} Eventually this other one did work: {:find '[e] :where [(depends e) (not (doesn't-depend e))] :rules [[(depends e) [e :dependencies d1] [(== deps d1)]] [(doesn't-depend e) [e :dependencies d2] [(!= deps d2)]]] :args [{'deps #{:dep-1}]} I think it's because the rules in the last one create subsets of the entity, rather than creating subsets of tuples of the entity and a dependency, like the ones that didn't work. Hence the question about sub-queries. I'm guessing that each rule generates a subset on it's own, and then the final query is the intersection of the various tuples?

In that first snippet are you missing a # ? Is that value for :dependencies supposed to be a set?

...assuming so, I think you should be able to do this: {:find [e] :where [[e :dependencies :dep1] (not [e :dependencies :dep2])}

@US65YEL1M (just making sure you don't miss this response!)