av-scan.clj

av-scan.clj

(let [n (xt/start-node {})
      _ (xt/await-tx n (xt/submit-tx n [[::xt/put {:xt/id 0 :k 0}]
                                        [::xt/put {:xt/id 1 :k 0}]
                                        [::xt/put {:xt/id 2 :k 0}]
                                        [::xt/put {:xt/id 3 :k 1}]
                                        [::xt/put {:xt/id 4 :k 2}]
                                        [::xt/put {:xt/id 5 :k 2}]
                                        [::xt/put {:xt/id 6 :k 3}]]))]
  (with-open [r (xt/open-q (xt/db n)
                           '{:find [v]
                             :where [[_ :k v]]})]
    (take 10 (iterator-seq r)))
  ;;=> ([0] [0] [0] [1] [2] [2] [3])
  ;; ideally this might just return a scan over AV, but XT isn't doing that today (2021-09-11)
  ;; it is potentially a optimisation/heuristic we could support in future

  ;; raw access to AV is possible anyway though
  (with-open [db (xt/open-db n)]
    (with-open [is (db/open-index-snapshot (:index-store db))]
      (doall (map xtdb.codec/decode-value-buffer (take 10 (xtdb.db/av is :k nil))))))
  ;;=> (0 1 2 3)
  )