perf(backend): avoid N+1 selects from `user` table when packing many entities (#13911)

* perf(backend): avoid N+1 selects from `user` table when packing many entities

* perf(backend): use `packMany` instead of mapping to `pack`

2 files changed, 9 insertions, 7 deletions

diff --git a/packages/backend/src/server/api/endpoints/users/get-frequently-replied-users.ts b/packages/backend/src/server/api/endpoints/users/get-frequently-replied-users.ts
index 02aa037466..9248a2fa68 100644
--- a/packages/backend/src/server/api/endpoints/users/get-frequently-replied-users.ts
+++ b/packages/backend/src/server/api/endpoints/users/get-frequently-replied-users.ts
@@ -118,12 +118,14 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			const repliedUsersSorted = Object.keys(repliedUsers).sort((a, b) => repliedUsers[b] - repliedUsers[a]);
 
 			// Extract top replied users
-			const topRepliedUsers = repliedUsersSorted.slice(0, ps.limit);
+			const topRepliedUserIds = repliedUsersSorted.slice(0, ps.limit);
 
 			// Make replies object (includes weights)
-			const repliesObj = await Promise.all(topRepliedUsers.map(async (user) => ({
-				user: await this.userEntityService.pack(user, me, { schema: 'UserDetailed' }),
-				weight: repliedUsers[user] / peak,
+			const _userMap = await this.userEntityService.packMany(topRepliedUserIds, me, { schema: 'UserDetailed' })
+				.then(users => new Map(users.map(u => [u.id, u])));
+			const repliesObj = await Promise.all(topRepliedUserIds.map(async (userId) => ({
+				user: _userMap.get(userId) ?? await this.userEntityService.pack(userId, me, { schema: 'UserDetailed' }),
+				weight: repliedUsers[userId] / peak,
 			})));
 
 			return repliesObj;
diff --git a/packages/backend/src/server/api/endpoints/users/show.ts b/packages/backend/src/server/api/endpoints/users/show.ts
index 26cfa921c5..062326e28d 100644
--- a/packages/backend/src/server/api/endpoints/users/show.ts
+++ b/packages/backend/src/server/api/endpoints/users/show.ts
@@ -117,9 +117,9 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 					if (user != null) _users.push(user);
 				}
 
-				return await Promise.all(_users.map(u => this.userEntityService.pack(u, me, {
-					schema: 'UserDetailed',
-				})));
+				const _userMap = await this.userEntityService.packMany(_users, me, { schema: 'UserDetailed' })
+					.then(users => new Map(users.map(u => [u.id, u])));
+				return _users.map(u => _userMap.get(u.id)!);
 			} else {
 				// Lookup user
 				if (typeof ps.host === 'string' && typeof ps.username === 'string') {