Small Datahike example

datahike_example.clj

(require '[datahike.api :as d])

(def schema [{:db/ident       :name
              :db/cardinality :db.cardinality/one
              :db/index       true
              :db/unique      :db.unique/identity
              :db/valueType   :db.type/string}
             {:db/ident       :parents
              :db/cardinality :db.cardinality/many
              :db/valueType   :db.type/ref}
             {:db/ident       :age
              :db/cardinality :db.cardinality/one
              :db/valueType   :db.type/long}])

(def cfg {:store              {:backend :mem
                               :id      "dev-2"}
          :keep-history?      true
          :schema-flexibility :write})

(do
  (d/delete-database cfg)
  (d/create-database cfg))

(def conn (d/connect cfg))

(d/transact conn schema)

(d/transact conn [{:name "Alice"
                   :age  25}
                  {:name "Bob"
                   :age  35}])

(d/transact conn [{:name    "Charlie"
                   :age     5
                   :parents [[:name "Alice"] [:name "Bob"]]}])

(d/transact conn [{:name "Daisy" :age 20}])
(d/transact conn [{:name "Erhard" :age 20}])
(d/transact conn [[:db/retractEntity [:name "Erhard"]]])


(->> (d/q '[:find ?e ?n ?a
            :where
            [?e :name ?n]
            [?e :age ?a]] @conn))
(d/q '[:find ?e ?n
       :where
       [?e :name ?n]] @conn)

(d/datoms @conn :eavt)

(d/transact conn {:tx-data [[:db/retractEntity [:name "Erhard"]]]})

(d/datoms @conn :eavt)