Datomic - update cardinality many attr

datomic-update-cardinality-many-attr.clj

(ns datomic-update-cardinality-many
  (:require [datomic.api :as d]))

(defn update-attr-txs [db entity-id attr values]
  (let [current-vals (-> (d/q '[:find [?p ...]
                                :where [?id :intention/parents ?p]
                                :in $ ?id]
                              db
                              entity-id)
                         (set))
        [added removed] (clojure.data/diff (set values) current-vals)]
    (concat (->> added
                 (map #(-> [:db/add entity-id attr %])))
            (->> removed
                 (map #(-> [:db/retract entity-id attr %]))))))