It seems there is a difference of the type of a query result between code executed locally in the repl and inside an ion.
The following code:
(defn test-datomic [_] (let [res (d/q '[:find ?ident :where [_ :db/ident ?ident]] (d/db (get-conn)))] (-> res type str)))
- “class clojure.lang.PersistentVector” locally
- “class java.util.HashSet” when deployed as an ion