Clean up database calls

src/computersandblues/lodestone/app.cljs

@@ -160,8 +160,9 @@
 (declare fetch-posts!)
 
 (defn- fetch-application-settings []
-  (->> (db/open-cursor ::db/application ::db/all)
-       (db/first-result (map #(js->clj % :keywordize-keys true)))))
+  (let [cursor (db/open-cursor ::db/application ::db/all)]
+    (. (db/first-result cursor)
+       (then #(js->clj % :keywordize-keys true)))))
 
 (defn setup-application!
   "Handles Mastodon application setup on the client side"
@@ -287,29 +288,32 @@
 
 (defn- refresh-displayed-posts!
   [{:keys [per-page query]}]
-  (let [; this `xform` is responsible for filtering and building the final list
-        ; of results by iterating through the posts in the database.
+  (let [; this `xform` is responsible for filtering and building the list of
+        ; results that is displayed to the user. it iterates through all stored
+        ; posts in the database and returns a result that will be rendered
+        ; by the `post` component below.
         xform (comp
                (filter (query->matching-fn query))
                (take per-page)
                (map #(js->clj % :keywordize-keys true)))
+        posts-cursor (db/open-cursor ::db/posts
+                                     ::db/all
+                                     {:index ::db/post-created-at
+                                      :direction :desc})
         refresh-id (now)]
     (swap! state update-in [:section/posts :loading] conj refresh-id)
     (. (promise-all [(db/count ::db/posts)
-                     (->> (db/open-cursor ::db/posts ::db/all
-                                          {:index ::db/post-created-at
-                                           :direction :desc})
-                          (db/transduce-cursor xform))])
+                     (db/transduce-cursor xform posts-cursor)])
        (then (fn [[total displayed-posts]]
                (swap! state update :section/posts #(-> (assoc % :total total)
                                                        (assoc :displayed-posts displayed-posts)
                                                        (update :loading disj refresh-id))))))))
 
+(def debounced-refresh! (debounce 48 refresh-displayed-posts!))
+
 ; we use reagent's machinery below to define a callback that runs whenever the
 ; values change that serve as input to the current search reults.
 
-(def debounced-refresh! (debounce 48 refresh-displayed-posts!))
-
 (def search-result-inputs (r/reaction (select-keys (:section/posts @state) [:query :per-page :last-update])))
 
 (defonce update-search-results (r/track! (fn []
@@ -378,14 +382,15 @@
   ; run and time a query on the database
   (do
     (js/console.log :start (.toISOString (js/Date.)))
-    (. (->> (db/open-cursor ::db/posts ::db/all)
-            (db/transduce-cursor (comp (mapcat (j/get :tags))
-                                       (map (j/get :name))
-                                       (filter #(= "typescript" %))
-                                       (take 50)) conj (sorted-set)))
-       (then (fn [result]
-               (js/console.log :end (.toISOString (js/Date.)))
-               (js/console.log :accts result)))))
+    (let [xform (comp (mapcat (j/get :tags))
+                      #_(filter #(= "typescript" (j/get % :name)))
+                      (take 10))
+          posts-cursor (db/open-cursor ::db/posts ::db/all)]
+      (.. (db/transduce-cursor xform conj! (transient #{}) posts-cursor)
+          (then persistent!)
+          (then (fn [result]
+                  (js/console.log :end (.toISOString (js/Date.)))
+                  (js/console.log :accts result))))))
   )
 
 (defn post [{:keys [post]}]
@@ -450,9 +455,9 @@
   "Returns a promise which resolves to the smallest or largest internal post id.
   This is useful to continue interrupted paginated requests."
   [max-or-min]
-  (->> (db/open-cursor ::db/posts ::db/all {:index ::db/post-internal-id
-                                            :direction (if (= max-or-min :min) :asc :desc)})
-       (db/first-result (keep (j/get :internal_id)))))
+  (let [posts-cursor (db/open-cursor ::db/posts ::db/all {:index ::db/post-internal-id
+                                                          :direction (if (= max-or-min :min) :asc :desc)})]
+    (db/first-result (keep (j/get :internal_id)) posts-cursor)))
 
 (defn- fetch-more-posts! [e]
   (.preventDefault e)
@@ -553,11 +558,11 @@
 
 (defn- convert-internal-ids! []
   ; TODO figure out when we can remove this again
-  (. (->> (db/open-cursor ::db/posts ::db/all)
-          (db/transduce-cursor (filter (comp string? (j/get :internal_id)))))
-     (then (fn [rows]
-              (doseq [row rows]
-                (db/put! ::db/posts (j/update! row :internal_id parse-long)))))))
+  (let [cursor (db/open-cursor ::db/posts ::db/all)
+        result (db/transduce-cursor (filter (comp string? (j/get :internal_id))) cursor)]
+    (.then result (fn [rows]
+                    (doseq [row rows]
+                      (db/put! ::db/posts (j/update! row :internal_id parse-long)))))))
 
 ;; go go go
 

src/computersandblues/lodestone/database.cljs

@@ -161,8 +161,15 @@
                                      (.continue cursor))))
                                (resolve @result)))))))))
 
-(defn first-result [xform cursor-req]
-  (transduce-cursor (comp xform (take 1)) (fn [_ x] x) nil cursor-req))
+(defn first-result
+  "Given a cursor, will return a promise that resolves to the first result.
+
+  Optionally takes an `xform` that can be used to filter or transform values
+  returned by the cursor."
+  ([cursor-req]
+   (first-result (map identity) cursor-req))
+  ([xform cursor-req]
+   (transduce-cursor (comp xform (take 1)) (fn [_ x] x) nil cursor-req)))
 
 (comment