Clojurians Log v2

Is there a way to get the following transaction to pass without first transacting {:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")} in this example?

(def schema
  {:user/id {:db/unique :db.unique/identity}
   :user/bots {:db/valueType :db.type/ref
               :db/cardinality :db.cardinality/many}
   :bot/id {:db/unique :db.unique/identity}
   :bot/created-by {:db/type :db.type/ref
                    :db/cardinality :db.cardinality/one}})

;; Transaction fails with:
;; "Cannot add #datascript/Datom [5 :user/id #uuid "a9d9494b-9c96-4e14-8bc5-999a11651358" 536870922 true] because of unique constraint: (#datascript/Datom [7 :user/id #uuid "a9d9494b-9c96-4e14-8bc5-999a11651358" 536870922 true])"

[{:user/bots [{:bot/id (uuid "5ae358f2-5a0c-49ff-9868-bb4f6aa5e98d")
               :bot/created-by {:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}}]
  :user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}]

;; Transaction succeeds

[{:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}
 {:user/bots [{:bot/id (uuid "5ae358f2-5a0c-49ff-9868-bb4f6aa5e98d")
               :bot/created-by {:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}}]
  :user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}]

I note that :bot/id is malformed; the key is :db/valueType, not :db/type. but that's probably unrelated.

to answer your actual question: use a lookup ref instead. the duplicated {:user/id (uuid "a9d9...")} is making it try to create two users with the same ID.

so the top-level :user/id (uuid "a9d9...") is good. then inside the :user/bots use a lookup :bot/created-by [:user/id (uuid "a9d9...")].

also, stepping back and looking at the design more broadly: don't model relationships in both directions.

this is what the VAET index is for: reverse ref lookups.

if the bots have :bot/created-by as a ref to the user, you can write queries like

(q '[:find [?bot ...] :in $ ?id
      :where [?user :user/id ?]
            [?bot :bot/created-by ?user]]
  db (uuid "a9d9..."))

;; "Nothing found for entity id [:user/id #uuid "a9d9494b-9c96-4e14-8bc5-999a11651358"]"
{:user/bots [{:bot/id (uuid "5ae358f2-5a0c-49ff-9868-bb4f6aa5e98d")
                              :bot/created-by [:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")]}]
                 :user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}

Corrected the schema and updated the ref but got ^. Transacting {:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")} first works as well using the ref.

@oconn see the remarks about the data modeling. I encourage you to drop the :user/bots field outright. then you can transact

[{:user/id (uuid "a9d9...")}
 {:bot/id  (uuid "5ae3...")
  :bot/created-by [:user/id (uuid "a9d9...")]
 }]

(and lose nothing in queryability)

Yeah, that’s the next path I was going to walk. The reason I’m trying to get it to work this way is because I’m using a graph api and that’s the way the data was requested. It would be nice to directly transact the response.

well, you'll have to massage it somewhat to use the lookup ref anyway, so it's already not a drop-in.

Rough draft idea to solve for that;

(defn- xform-metadata
  [[entity-key entity-value]]
  (let [entity-name (name entity-key)]
    (if (and (#{"created-by" "updated-by" "deleted-by"} entity-name)
             (some? (:user/id entity-value)))
      [entity-key [:user/id (:user/id entity-value)]]
      [entity-key entity-value])))

(defn- clean-transaction
  "Cleans a datascript transaction before insertion"
  [transaction]
  (walk/postwalk
   (fn [x]
     (if (map? x)
       (->> x
            (remove (fn [[_entity-key entity-value]]
                      (case entity-value
                        nil true
                        :com.wsscode.pathom.core/not-found true
                        false)))
            (map xform-metadata)
            (into {}))
       x))
   transaction))

Which would get run on each transaction. Not 100% how I feel about this quite yet..

hm. it's hard to say without seeing the input data, it feels a bit awkward, relative to writing specific code to destructure a particular input map and build a transaction from it.

and you could add a further step to the transformation to select-keys, so you only get the ones you want and not eg. :user/bots.

Kinda doing something similar when requesting data. Maybe this will help describe the use case a little more.

;; Pathom query to server
{[:user/id user-uuid]
 (into [{:user/bots bots-db/bot-keys}]
   (remove #{:user/bots} users-db/user-keys))}

[{:user/bots [{:bot/id (uuid "5ae358f2-5a0c-49ff-9868-bb4f6aa5e98d")
               :bot/created-by {:user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}}]
  :user/id (uuid "a9d9494b-9c96-4e14-8bc5-999a11651358")}] 

Thanks again for taking time and looking through this @braden.shepherdson

well, you can model the relationship the other way if you want (`:user/bots` is a list of bots that are assumed to have been created by their owning user) but it's a little more awkward that way.

then the only transformation you need to make is to dissoc :bot/created-by outright.