tuples2.clj

(ns dato.tuples2
  (:require [datomic.api :as d])) ; Datomic pro 0.9.6024

(def url "datomic:mem://test-db")

(def conn (do (d/delete-database url)
              (d/create-database url)
              (d/connect url)))

(def schema
  [{:db/ident :student/first
    :db/valueType :db.type/string
    :db/cardinality :db.cardinality/one}
   {:db/ident :student/last
    :db/valueType :db.type/string
    :db/cardinality :db.cardinality/one}
   {:db/ident :student/email
    :db/valueType :db.type/string
    :db/cardinality :db.cardinality/one
    :db/unique :db.unique/identity}
   {:db/ident :semester/year
    :db/valueType :db.type/long
    :db/cardinality :db.cardinality/one}
   {:db/ident :semester/season
    :db/valueType :db.type/keyword
    :db/cardinality :db.cardinality/one}
   {:db/ident :semester/year+season
    :db/valueType :db.type/tuple
    :db/tupleAttrs [:semester/year :semester/season]
    :db/cardinality :db.cardinality/one
    :db/unique :db.unique/identity}
   {:db/ident :course/id
    :db/valueType :db.type/string
    :db/unique :db.unique/identity
    :db/cardinality :db.cardinality/one}
   {:db/ident :course/name
    :db/valueType :db.type/string
    :db/cardinality :db.cardinality/one}

   {:db/ident :reg/course
    :db/valueType :db.type/ref
    :db/cardinality :db.cardinality/one}
   {:db/ident :reg/semester
    :db/valueType :db.type/ref
    :db/cardinality :db.cardinality/one}
   {:db/ident :reg/student
    :db/valueType :db.type/ref
    :db/cardinality :db.cardinality/one}

   {:db/ident :reg/course+semester+student
    :db/valueType :db.type/tuple
    :db/tupleAttrs [:reg/course :reg/semester :reg/student]
    :db/cardinality :db.cardinality/one
    :db/unique :db.unique/identity}])

@(d/transact conn schema)

@(d/transact conn [{:semester/year 2018
                    :semester/season :fall}
                   {:course/id "BIO-101"}
                   {:student/first "John"
                    :student/last "Doe"
                    :student/email "[email protected]"}])

@(d/transact conn [{:reg/course [:course/id "BIO-101"]
                    :reg/semester [:semester/year+season [2018 :fall]]
                    :reg/student [:student/email "[email protected]"]}])

(defn db-id [lookup-ref]
  (d/q '[:find ?e .
         :in $ ?id-attr ?value
         :where
         [?e ?id-attr ?value]]
       (d/db conn)
       (first lookup-ref)
       (second lookup-ref)))

(comment
  (d/q '[:find (pull ?e [*]) .
         :in $ ?course-semester-student
         :where
         [?e :reg/course+semester+student ?course-semester-student]]
        (d/db conn)
       [(db-id [:course/id "BIO-101"])
        (db-id [:semester/year+season [2018 :fall]])
        (db-id [:student/email "[email protected]"])]))
  ; =>
  ;{:db/id 17592186045422,
  ; :reg/course #:db{:id 17592186045419},
  ; :reg/semester #:db{:id 17592186045418},
  ; :reg/student #:db{:id 17592186045420},
  ; :reg/course+semester+student [17592186045419 17592186045418 17592186045420]}