From 91fe01f2476a94d30026749927aafcc9f524ea53 Mon Sep 17 00:00:00 2001
From: moonrailgun <moonrailgun@gmail.com>
Date: Thu, 22 Dec 2022 00:33:14 +0800
Subject: [PATCH] =?UTF-8?q?perf:=20=E4=BC=98=E5=8C=96fetchConverseLastMess?=
 =?UTF-8?q?ages=E6=9F=A5=E8=AF=A2=E8=AF=AD=E5=8F=A5=EF=BC=8C=E9=98=B2?=
 =?UTF-8?q?=E6=AD=A2=E6=95=B0=E6=8D=AE=E9=87=8F=E8=BF=87=E5=A4=A7=E5=AF=BC?=
 =?UTF-8?q?=E8=87=B4=E8=AF=B7=E6=B1=82=E8=B6=85=E6=97=B6?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 server/services/core/chat/message.service.ts | 47 ++++++++++----------
 1 file changed, 23 insertions(+), 24 deletions(-)

diff --git a/server/services/core/chat/message.service.ts b/server/services/core/chat/message.service.ts
index 43aab794..9601607d 100644
--- a/server/services/core/chat/message.service.ts
+++ b/server/services/core/chat/message.service.ts
@@ -260,32 +260,31 @@ class MessageService extends TcService {
    */
   async fetchConverseLastMessages(ctx: TcContext<{ converseIds: string[] }>) {
     const { converseIds } = ctx.params;
-    const list = await this.adapter.model
-      .aggregate<{
-        _id: string;
-        lastMessageId: string;
-      }>([
-        {
-          $match: {
-            converseId: {
-              $in: converseIds.map((id) => new Types.ObjectId(id)),
-            },
-          },
-        },
-        {
-          $group: {
-            _id: '$converseId' as any,
-            lastMessageId: {
-              $last: '$_id',
+
+    // 这里使用了多个请求，但是通过limit=1会将查询范围降低到最低
+    const list = await Promise.all(
+      converseIds.map((id) => {
+        return this.adapter.model
+          .findOne(
+            {
+              converseId: new Types.ObjectId(id),
             },
-          },
-        },
-      ])
-      .exec();
+            {
+              _id: 1,
+              converseId: 1,
+            }
+          )
+          .sort({
+            _id: -1,
+          })
+          .limit(1)
+          .exec();
+      })
+    );
 
-    return list.map((item) => ({
-      converseId: item._id,
-      lastMessageId: item.lastMessageId,
+    return list.filter(Boolean).map((item) => ({
+      converseId: String(item.converseId),
+      lastMessageId: String(item._id),
     }));
   }