feat: optimize db queries (#297)

src/sources/scheduler.service.ts

@@ -53,7 +53,7 @@ export class SchedulerService implements OnApplicationBootstrap {
     const INACTIVE_CUTOFF_MSEC = 60 * 60 * 1000;
 
     await Promise.all(
-      userInfo.map(({ user, lastListen }) => {
+      userInfo.map(({ userID, lastListen }) => {
         let pollRate = POLL_RATE_INACTIVE_SEC;
 
         const timeSinceLastListen = new Date().getTime() - lastListen.getTime();
@@ -62,10 +62,10 @@ export class SchedulerService implements OnApplicationBootstrap {
         }
 
         this.importSpotifyJobService.sendThrottled(
-          { userID: user.id },
+          { userID },
           {},
           pollRate,
-          user.id,
+          userID,
         );
       }),
     );

src/sources/spotify/spotify.service.ts

@@ -43,27 +43,31 @@ export class SpotifyService {
   ) {}
 
   @Span()
-  async getCrawlableUserInfo(): Promise<{ user: User; lastListen: Date }[]> {
-    // All of this is kinda inefficient, we do two db queries and join in code,
-    // i can't be bothered to do this properly in the db for now.
-    // Should be refactored if listory gets hundreds of users (lol).
+  async getCrawlableUserInfo(): Promise<
+    { userID: string; lastListen: Date }[]
+  > {
+    const users = await this.usersService
+      .getQueryBuilder()
+      .select(`user.id as "userID"`)
+      .addSelect(`listen."playedAt" as "lastListen"`)
+      .leftJoin(
+        (qb) =>
+          qb
+            .distinctOn(["listen.userId"])
+            .select(`listen."userId"`)
+            .addSelect(`listen."playedAt"`)
+            .from("listen", "listen")
+            .orderBy("listen.userId", "DESC")
+            .addOrderBy("listen.playedAt", "DESC"),
+        "listen",
+        `listen."userId" = user.id`,
+      )
+      .getRawMany<{ userID: string; lastListen?: Date }>();
 
-    const [users, listens] = await Promise.all([
-      this.usersService.findAll(),
-      this.listensService.getMostRecentListenPerUser(),
-    ]);
-
-    return users.map((user) => {
-      const lastListen = listens.find((listen) => listen.user.id === user.id);
-
-      return {
-        user,
-        // Return 1970 if no listen exists
-        lastListen: lastListen ? lastListen.playedAt : new Date(0),
-      };
-    });
-
-    return;
+    return users.map(({ userID, lastListen }) => ({
+      userID,
+      lastListen: lastListen || new Date(0),
+    }));
   }
 
   @ImportSpotifyJob.Handle()