how do you enforce constraints in datomic cloud?

what kind of constraints do you mean?

like a payment can be registered only if a customer exists

I have a mechanism for doing this, but there's nothing built in to Datomic.

Essentially, I have a transaction function that runs in the transactor, and it gets passed the tx. It uses d/with to build a db with the tx, then enumerates the constraints queries in the database, and ensures that none of them return data.

If successful, it returns the tx as-is. Otherwise, it fails with a nice error message.

I'm looking for things to extract from my (overly large) project. Perhaps this is a nice thing.

ah, you pass custom code to the transactor, is this supported in cloud?

Hmm... I don't know. I mean, I'll bet you can install transaction functions, but I don't know much about cloud.

Afaik no custom transaction function on cloud.

hmm true, looks like is not supported https://docs.datomic.com/on-prem/moving-to-cloud.html#sec-4

This will be an evolving area of cloud

@alexmiller do you have a rough timeframe for this?

no