Removing entities

[julienfantin]

Removing entities can be achieved with (dissoc db (ref-to db my-entity)).

This is undocumented and it is a subtle operation, because:

• It will leave dangling refs in entities who join my-entity
• During query parsing pull ignores refs and colls of refs that do not resolve
• Essentially using pull gives the expected result, but the db is an inconsistent state.

If db-level consistency is desirable, we could maintain an index during add and remove that'd allow a fast reverse lookup on the removed ref, to the refs and attributes pointing to it:

{<ingress-ref> {<egress-ref> <from-attr>}}

This would give us a add and remove operations in time linear to the number of joins.