Add bulk rating fetching

src/utils/queryCacher.ts

@@ -10,6 +10,7 @@ async function get<T>(fetchFromDB: () => Promise<T>, key: string): Promise<T> {
     if (!err && reply) {
         try {
             Logger.debug(`Got data from redis: ${reply}`);
+
             return JSON.parse(reply);
         } catch (e) {
             // If all else, continue on to fetching from the database
@@ -22,6 +23,53 @@ async function get<T>(fetchFromDB: () => Promise<T>, key: string): Promise<T> {
     return data;
 }
 
+/**
+ * Gets from redis for all specified values and splits the result before adding it to redis cache
+ */
+async function getAndSplit<T, U>(fetchFromDB: (values: U[]) => Promise<Array<T>>, keyGenerator: (value: U) => string, splitKey: string, values: U[]): Promise<Array<T>> {
+    const cachedValues = await Promise.all(values.map(async (value) => {
+        const key = keyGenerator(value);
+        const { err, reply } = await redis.getAsync(key);
+
+        if (!err && reply) {
+            try {
+                Logger.debug(`Got data from redis: ${reply}`);
+
+                return {
+                    value,
+                    result: JSON.parse(reply)
+                };
+            } catch (e) {
+                // eslint-disable-next-line no-console
+            }
+        }
+
+        return {
+            value,
+            result: null
+        };
+    }));
+
+    const data = await fetchFromDB(
+        cachedValues.filter((cachedValue) => cachedValue.result === null)
+            .map((cachedValue) => cachedValue.value));
+
+    new Promise(() => {
+        const newResults: Record<string, T[]> = {};
+        for (const item of data) {
+            const key = (item as unknown as Record<string, string>)[splitKey];
+            newResults[key] ??= [];
+            newResults[key].push(item);
+        }
+
+        for (const key in newResults) {
+            redis.setAsync(keyGenerator(key as unknown as U), JSON.stringify(newResults[key]));
+        }
+    });
+
+    return data.concat(cachedValues.map((cachedValue) => cachedValue.result).filter((result) => result !== null));
+}
+
 function clearSegmentCache(videoInfo: { videoID: VideoID; hashedVideoID: VideoIDHash; service: Service; userID?: UserID; }): void {
     if (videoInfo) {
         redis.delAsync(skipSegmentsKey(videoInfo.videoID, videoInfo.service));
@@ -38,6 +86,7 @@ function clearRatingCache(videoInfo: { hashedVideoID: VideoIDHash; service: Serv
 
 export const QueryCacher = {
     get,
+    getAndSplit,
     clearSegmentCache,
     clearRatingCache
 };