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clojuredatomicdatalogdatascript

How to query against attributes of multiple values?

Tested on datascript 1.3.0

datoms:

[{:db/id -1 :name "Oliver Smith" :hobbies ["reading" "sports" "music"]}]

tried to run the query below to find who like sports, but the empty set returned.

'[:find ?name
  :where
  [?p :name ?name]
  [?p :hobbies ?hobbies]
  [(some #{"sports"} ?hobbies)]]

How to formulate the query correctly to get the expected result below?

#{[Oliver Smith]}
Solution

  • We have to explicitly define the schema with cardinality/many against the attribute of multiple values to solve the problem since schemaless doesn't work here.

    (require '[datascript.core :as d])

(def schema {:hobbies {:db/cardinality db.cardinality/many}})
(def conn (d/create-conn schema))

(def datoms [{:db/id -1 :name "Oliver Smith" :hobbies ["reading" "sports" "music"]}])
(d/transact! conn datoms)

(def query '[:find ?name :where [?p :name ?name] [?p :hobbies "sports"]])
(-> (d/q query @conn) println)