datomic-clojure-relational-algebra-2012-07-07

gistfile1.clj

(ns mynamespace.dt
  (:use clojure.set)

  (:use [datomic.api :only [q db] :as d])
  (:use clojure.pprint)
  )

;;; http://www.lshift.net/blog/2010/08/21/some-relational-algebra-with-datatypes-in-clojure-12

(defrecord Supplier [number name status city])
;;;(-> Supplier .getConstructors first .getParameterTypes)
;;;(Supplier/getBasis)
(defrecord Part [number name colour weight city])
(defrecord Shipment [supplier part quantity])

(def suppliers
  #{(Supplier. "S1" "Smith" 20 "London")
    (Supplier. "S2" "Jones" 10 "Paris")
    (Supplier. "S3" "Blake" 30 "Paris")})

(def parts
  #{(Part. "P1" "Nut" "Red" 12.0 "London")
    (Part. "P2" "Bolt" "Green" 17.0 "Paris")
    (Part. "P3" "Screw" "Blue" 17.0 "Oslo")})

(def shipments
  #{(Shipment. "S1" "P1" 300)
    (Shipment. "S2" "P2" 200)
    (Shipment. "S2" "P3" 400)})
;;;(rename parts {:number :id :city :location})
;;;(select (fn [imap] (= (:name imap) "Smith")) suppliers)
;;;(project suppliers [:city])
;;;(join parts shipments {:number :part})
;;;(project (join (select #(= (:city %) "Paris") suppliers) shipments {:number :supplier}) [:name])

;;; http://stackoverflow.com/questions/2852133/clojure-vars-and-java-static-methods
;;; {:number "S1", :name "Smith", :status 20, :city "London"} -> ["S1" "Smith" 20 "London"]
(defn map-relation [record-id relation]
  (let [basis (. (. record-id getMethod "getBasis" (make-array Class 0)) invoke nil (make-array Object 0))]
    (into []
          (map (fn [entry]
                 (into []
                       (map (fn [sym]
                              (get entry (keyword sym)))
                            basis)))
               relation))))
;;;(map-relation Supplier suppliers)

(defn test-datomic-query-2 []
  (q '[:find ?supplier-name
       :in [[?supplier-number ?supplier-name ?supplier-status ?supplier-city]]
       :where [(= ?supplier-city "Paris")]
       ]
     (map-relation Supplier suppliers)
     ))
;;;(test-datomic-query-2)

(defn test-datomic-query-3 []
  (q '[:find ?supplier-name
       :in $suppliers
       :where [$suppliers _ ?supplier-name _ "Paris"]
       ]
     (map-relation Supplier suppliers)
     ))
;;;(test-datomic-query-3)

(defn test-datomic-query-4 []
  (q '[:find ?supplier-name
       :in $suppliers $shipments
       :where
       [$suppliers ?supplier-number ?supplier-name ?supplier-status "Paris"]
       [$shipments ?supplier-number ?shipment-part ?shipment-quantity]
       ]
     (map-relation Supplier suppliers)
     (map-relation Shipment shipments)
     ))
;;;(test-datomic-query-4)