本文介绍了$ lookup并推送新数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个讨论对象集合，一个用户死亡集合.
Hi i'm having a discussion object collection and a user deatils collection.
讨论集合将参与者用户名存储在字符串数组中.讨论集合如下:
Discussion collection stores the participants username in an array of strings.Discussion collection is as follows:
[{ "_id": "5a4dbdaab46b426863e7ead3",
"topic": "test",
"topicDesc": "test123",
"createdOn": "2018-01-04T05:37:46.088Z",
"participants": ["akhil","ben"] //[usernames]
}]
用户详细信息收集如下:
The user details collection is as follows:
[{
"_id": "59e6d6ba02e11e1814481022",
"username": "ben",
"name": "Ben S",
"email": "qwerty@123.com",
},{
"_id": "5a0431b1d6fab00cdf484677",
"username": "akhil",
"name": "Akhil Clement",
"email": "qwerty@123.com",
}]
结果JSON就像
[{ "_id": "5a4dbdaab46b426863e7ead3",
"topic": "test",
"topicDesc": "test123",
"createdOn": "2018-01-04T05:37:46.088Z",
"participants": ["akhil","ben"] //[usernames]
"participantDetails": [{
"_id": "59e6d6ba02e11e1814481022",
"username": "ben",
"name": "Ben S",
"email": "qwerty@123.com",
},{
"_id": "5a0431b1d6fab00cdf484677",
"username": "akhil",
"name": "Akhil Clement",
"email": "qwerty@123.com",
}]
}]
推荐答案
您需要使用用户集合和$group
you need to $lookup with user collection and $group
db.dis.aggregate(
[
{$unwind : "$participants"},
{$lookup : {from : "us", localField : "participants", foreignField : "username", as : "userData"}},
{$group : {_id : {
_id : "$_id", topic : "$topic", topicDesc : "$topicDesc", createdOn : "$createdOn"
},
participants : {$push : "$participants" } ,
participantDetails : {$push : {$arrayElemAt : ["$userData", 0]}}}
},
{$project : {
_id : "$_id._id",
topic : "$_id.topic",
topicDesc : "$_id.topicDesc",
createdOn : "$_id.createdOn",
participants : 1 ,
participantDetails : 1
}}
]
).pretty()
结果
{
"participants" : [
"akhil",
"ben"
],
"participantDetails" : [
{
"_id" : "59e6d6ba02e11e1814481020",
"username" : "akhil",
"name" : "Akhil Clement",
"email" : "qwerty@123.com"
},
{
"_id" : "59e6d6ba02e11e1814481021",
"username" : "ben",
"name" : "Ben S",
"email" : "qwerty@123.com"
}
],
"_id" : "5a4dbdaab46b426863e7ead3",
"topic" : "test",
"topicDesc" : "test123",
"createdOn" : "2018-01-04T05:37:46.088Z"
}
编辑
将$push更改为$addToSet以避免重复
这篇关于$ lookup并推送新数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！