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(ns datascript-diff | |
(:require [datascript.core :as d] | |
[datascript.btset :as btset])) | |
(defn- keys-eq? [a b] | |
(or (identical? (.-keys a) (.-keys b)) | |
(let [achunk (btset/iter-chunk a) | |
bchunk (btset/iter-chunk b)] | |
(and (== (count achunk) (count bchunk)) | |
(every? #(= (nth achunk %) | |
(nth bchunk %)) | |
(range (count achunk))))))) | |
(defn datom-exists? [db datom] | |
(let [e (.-e datom) | |
a (.-a datom) | |
v (.-v datom)] | |
(not-empty (d/datoms db :eavt e a v)))) | |
(defn add-retract [action datom] | |
[action (.-e datom) (.-a datom) (.-v datom)]) | |
(defn datoms-diff | |
"Given two datascript dbs, return the :db/add :db/retract statements to bring them in sync" | |
([a-db b-db] (datoms-diff a-db b-db (d/datoms a-db :eavt) (d/datoms b-db :eavt) [])) | |
([a-db b-db a b accum] | |
(if (and (nil? a) (nil? b)) | |
accum | |
(if (and (some? a) (some? b) (keys-eq? a b)) | |
(recur a-db b-db (btset/iter-chunked-next a) (btset/iter-chunked-next b) accum) | |
(let [achunk (btset/iter-chunk a) | |
bchunk (btset/iter-chunk b) | |
diff (map (fn [x] | |
(let [a-datom (nth achunk x) | |
b-datom (nth bchunk x) | |
same? (= a-datom b-datom)] | |
(when-not same? | |
(cond-> [] | |
;; If a exists, but b doesn't, then we need to add a | |
(and a-datom (nil? b-datom) (not (datom-exists? b-db a-datom))) | |
(conj (add-retract :db/add a-datom)) | |
;; if b exists, but a doesn't, then we need to add b | |
(and b-datom (nil? a-datom) (not (datom-exists? a-db b-datom))) | |
(conj (add-retract :db/add b-datom)) | |
;; if a and b exist, but a isn't in b-db, then issue a retraction | |
(and a-datom b-datom (not (datom-exists? b-db a-datom))) | |
(conj (add-retract :db/retract a-datom)) | |
;; if a and b exist, but b isn't in a-db, then issue an addition | |
(and a-datom b-datom (not (datom-exists? a-db b-datom))) | |
(conj (add-retract :db/add b-datom)))))) | |
(range 25)) | |
filtered (filter not-empty diff) | |
merged (mapcat into filtered)] | |
(recur a-db b-db (btset/iter-chunked-next a) (btset/iter-chunked-next b) (into accum merged))))))) | |
(defn simple-test [] | |
(let [sample-db (-> (d/empty-db {:first-name {:db/index true} | |
:last-name {:db/index true} | |
:phone {:db/index true} | |
:email {:db/index true}}) | |
(d/db-with [[:db/add 1 :first-name "Sean"] | |
[:db/add 1 :last-name "Tempesta"] | |
[:db/add 1 :phone "555-5555"]])) | |
changes [[:db/add 1 :email "sean.tempesta@gmail.com"] | |
[:db/retract 1 :last-name "Tempesta"] | |
[:db/retract 1 :phone "555-5555"] | |
[:db/add 1 :phone "555-1234"]] | |
changed-db (d/db-with sample-db changes)] | |
(= changes (datoms-diff sample-db changed-db)))) |
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