Possible to get enum value via Datomic pull syntax?

Question

In the mbrainz sample data, the :artist/type is an enum. Is it possible to pull the value of the enum out of :db/ident and associate it as the value of the :artist/type key using pull syntax?

This is as close as I could get:

[:find (pull ?e [:artist/name {:artist/type [:db/ident]}]) :where [?e :artist/name "Ray Charles"] ] ;;=> [[{:artist/name "Ray Charles", :artist/type {:db/ident :artist.type/person}}]]

Is it possible to use pull syntax to reshape the result into something like this?

;;=> [[{:artist/name "Ray Charles", :artist/type :artist.type/person}]]

Alan Thompson · Accepted Answer · 2016-06-10 22:46:31Z

I don't think you can do it using the Pull API the way you are seeking. You may find that it is easier to use the Tupelo Datomic library:

(require '[tupelo.datomic :as td] '[tupelo.core :refer [spyx]] ) (let [x1 (td/query-scalar :let [$ db-val] :find [ ?e ] :where [ [?e :artist/name "Ray Charles"] ] ) x2 (td/entity-map db-val x1) ] (spyx x1) (spyx x2) )

which gives the result:

x1 => 17592186049074

x2 => {:artist/sortName "Charles, Ray", :artist/name "Ray Charles", :artist/type :artist.type/person, :artist/country :country/US, :artist/gid #uuid "2ce02909-598b-44ef-a456-151ba0a3bd70", :artist/startDay 23, :artist/endDay 10, :artist/startYear 1930, :artist/endMonth 6, :artist/endYear 2004, :artist/startMonth 9, :artist/gender :artist.gender/male}

So :artist/type is already converted into the :db/ident value and you can just pull it out of the map.

Chris Murphy · Accepted Answer · 2020-10-23 08:55:33Z

You can use specter on the result that the pull expression returns:

(->> pull-result (sp/transform (sp/walker :db/ident) :db/ident))

The value of key :db/ident is extracted for every map that has that key.

Max Prokopov · Accepted Answer · 2021-02-25 15:16:07Z

Was quite easy to do with postwalk

for any pulled :db/ident you can transform with this function

(defn flatten-ident [coll] (clojure.walk/postwalk (fn [item] (get item :db/ident item)) coll))

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