From 8410d4f96082592339d00ef8f83e2141eaeaafc8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8E=8B=E4=BA=9A=E7=90=AA?= <wangyaqi988@163.com>
Date: Fri, 10 Dec 2021 10:57:46 +0800
Subject: [PATCH] docs: uniCloud database aggregate

---
 docs/uniCloud/cf-database.md | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/docs/uniCloud/cf-database.md b/docs/uniCloud/cf-database.md
index 0bcc3d515..7ad5ac841 100644
--- a/docs/uniCloud/cf-database.md
+++ b/docs/uniCloud/cf-database.md
@@ -2067,6 +2067,31 @@ db.collection('scores').aggregate()
 
 **注意：聚合操作实例仅用于查询，不可执行增删改操作。在聚合操作实例上只能使用聚合操作方法，不能使用where/orderBy等基础方法，where需改为match，orderBy应使用sort实现，细节请阅读下方聚合操作文档。**
 
+云函数中使用时切勿复用aggregate实例，容易引发Bug。
+
+以下两种写法均为错误示例：
+
+```js
+const db = uniCloud.database()
+const collection = db.collection('test')
+const aggregate = collection.aggregate() // 云函数实例复用时，此聚合实例也会复用，导致Bug
+exports.main = async function(){
+  const res = await aggregate.match({a:1}).end()
+  return {res}
+}
+```
+
+```js
+const db = uniCloud.database()
+const collection = db.collection('test')
+exports.main = async function(){
+  const aggregate = collection.aggregate() // 此聚合实例分别在两个请求内使用，导致Bug
+  const res1 = await aggregate.match({a:1}).end()
+  const res2 = await aggregate.match({a:2}).end()
+  return {res1, res2}
+}
+```
+
 ### 聚合表达式
 
 表达式可以是字段路径、常量、或聚合操作符。表达式可以嵌套表达式。
-- 
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