Datomic or-join binding

or-join.clj

  (let [uri (str "datomic:mem://" (d/squuid))
        _ (d/create-database uri)
        conn (d/connect uri)
        schema [
                {:db/id #db/id[:db.part/db]
                 :db/ident :a/id
                 :db/valueType :db.type/uuid
                 :db/cardinality :db.cardinality/one
                 :db.install/_attribute :db.part/db}

                {:db/id #db/id[:db.part/db]
                 :db/ident :b/as
                 :db/valueType :db.type/ref
                 :db/cardinality :db.cardinality/many
                 :db.install/_attribute :db.part/db}

                {:db/id #db/id[:db.part/db]
                 :db/ident :b/id
                 :db/valueType :db.type/string
                 :db/cardinality :db.cardinality/one
                 :db.install/_attribute :db.part/db}

                {:db/id #db/id[:db.part/db]
                 :db/ident :c/b-id
                 :db/valueType :db.type/string
                 :db/cardinality :db.cardinality/one
                 :db.install/_attribute :db.part/db}

                ]

        data [
              {:db/id (d/tempid :db.part/user -1)
               :a/id (d/squuid)}

              {:db/id (d/tempid :db.part/user -2)
               :b/as #{(d/tempid :db.part/user -1)}
               :b/id "abc"}

              {:db/id (d/tempid :db.part/user -3)
               :c/b-id "abc"}
              ]
        ]
    @(d/transact conn schema)
    @(d/transact conn data)

    (let [db (d/db conn)
          ?a (->> (d/datoms db :aevt :a/id)
               (map :e)
               first)]
      (is (=

            ;; normal query
            (d/q '{:find [[?c ...]]
                   :in [$ ?a]
                   :where [[?b :b/as ?a]
                           [?b :b/id ?data-id]
                           [?c :c/b-id ?data-id]]}
                 (d/db conn) ?a)

            ;; query with or-join
            (d/q '{:find [[?c ...]]
                   :in [$ ?a]
                   :where [[?b :b/as ?a]
                           (or-join [?b]
                                    (and [?b :b/id ?data-id]
                                         [?c :c/b-id ?data-id]))]}
                 (d/db conn) ?a)))))