Postgres key transformations

postgres.clj

(ns postgres)

(require '[clojure.string :as str])
(require '[malli.core :as m])
(require '[malli.transform :as mt])

(defn -transform-keys [f m]
  (reduce-kv
    (fn [acc k v] (assoc acc (f k) v))
    (empty m)
    m))

(def upper-keys (partial -transform-keys (comp keyword str/upper-case name)))
(def lower-keys (partial -transform-keys (comp keyword str/lower-case name)))

;;
;; named property-driven transformations
;;

(def my-schema
  (m/schema
    [:map {:closed true
           :encode/postgres upper-keys
           :decode/postgres lower-keys}
     [:id             {:optional true
                       :postgres/type :bigserial
                       :postgres/key  :primary} int?]
     [:instrument-id  {:postgres/type :bigint
                       :postgres/null? false} int?]]))

(def postgres-transformer (mt/transformer {:name :postgres}))

(m/encode my-schema {:id 1, :instrument-id 2} postgres-transformer)
; => {:ID 1, :INSTRUMENT-ID 2}

(m/decode my-schema {:ID 1, :INSTRUMENT-ID 2} postgres-transformer)
; => {:id 1, :instrument-id 2}

;;
;; named transformations
;;

(def my-schema
  (m/schema
    [:map {:closed true
           :postgres/type :table}
     [:id             {:optional true
                       :postgres/type :bigserial
                       :postgres/key  :primary} int?]
     [:instrument-id  {:postgres/type :bigint
                       :postgres/null? false} int?]]))

(def postgres-transformer
  (let [t (fn [f] {:compile (fn [schema _]
                              (when (-> schema m/properties :postgres/type (= :table)) f))})]
    (mt/transformer
      {:name :postgres
       :decoders {:map (t lower-keys)}
       :encoders {:map (t upper-keys)}})))

(m/encode my-schema {:id 1, :instrument-id 2} postgres-transformer)
; => {:ID 1, :INSTRUMENT-ID 2}

(m/decode my-schema {:ID 1, :INSTRUMENT-ID 2} postgres-transformer)
; => {:id 1, :instrument-id 2}

;; no-op for other schemas
(m/decoder [:map [:x int?]] postgres-transformer)
; => #object[clojure.core$identity]