generic-range-value-inversion.clj

generic-range-value-inversion.clj

(require '[xtdb.memory :as xt-mem])
(require '[xtdb.codec :as xt-codec])

(defn v->buffer [v]
  (when (some? v)
    (xt-mem/as-buffer v)))

(defn v->ba [v]
  (xt-mem/->on-heap (xt-codec/->value-buffer v)))

(defn ba->v [ba]
  (xt-codec/decode-value-buffer (v->buffer ba)))

(defn bit-complement [ba]
  (byte-array (map bit-not ba)))

(defn ldt [^long i]
  (LocalDateTime/of 1 1 i 1 1 1 1))

(def node (xt/start-node {}))
(xt/submit-tx node
              (mapv #(vector ::xt/put (assoc %1
                                             :d (v->ba (:d %1))
                                             :d2 (-> (:d %1)
                                                     v->ba
                                                     bit-complement)))
                    [{:xt/id :a :i -7 :j 30 :d (ldt 17)}
                     {:xt/id :b :i 14 :j 25 :d (ldt 19)}
                     {:xt/id :c :i 14 :j 14 :d (ldt 19)}
                     {:xt/id :d :i 25 :j 14 :d (ldt 21)}
                     {:xt/id :e :i 30 :j -7 :d (ldt 22)}]))

(defn take-lt [db d n]
  (with-open [res (xt/open-q db
                             {:find '[e d2]
                              :where ['[e :d2 d2]
                                      [(list '< (v->ba d) 'd2 )]]})]
    (do (take n (map (fn mapper [[e d2]] (vector e (-> d2 bit-complement ba->v))) (iterator-seq res))))))

(xt/q (xt/db node)
      {:find '[e d2]
       :in '[d]
       :order-by '[[d2 :desc]] ; d2 relation gets reversed after take-lt returns (due to byte ordering) so we need to re-sort
       :limit 2
       :where '[[(dev/take-lt $ d 2) [[e d2]]]]}
      (ldt 23))
;;=> [[:e #object[java.time.LocalDateTime 0x525229aa "0001-01-22T01:01:01.000000001"]] [:d #object[java.time.LocalDateTime 0x2b82fda0 "0001-01-21T01:01:01.000000001"]]]