Node.js Mongodb聚合管道从数组返回多个带$lookup的字段
我试图通过createdAt从博士后文档中获取一个排序后的评论列表,其中聚合管道将用于使用displayName和profilePhoto字段填充comments in comments字段中评论的所有者 后架构:Node.js Mongodb聚合管道从数组返回多个带$lookup的字段,node.js,mongodb,express,mongoose,aggregation-framework,Node.js,Mongodb,Express,Mongoose,Aggregation Framework,我试图通过createdAt从博士后文档中获取一个排序后的评论列表,其中聚合管道将用于使用displayName和profilePhoto字段填充comments in comments字段中评论的所有者 后架构: { _owner: { type: Schema.Types.ObjectId, ref: 'User', required: true }, ... comments: [ { _owner: { type: Schema.Types.ObjectI
{
_owner: { type: Schema.Types.ObjectId, ref: 'User', required: true },
...
comments: [
{
_owner: { type: Schema.Types.ObjectId, ref: 'User' },
createdAt: Number,
body: { type: String, maxlength: 200 }
}
]
}
用户架构:
{
_id: '123abc'
profilePhoto: String,
displayName: String,
...
}
我想回报的是:
[
{
"_id": "5bb5e99e040bf10b884b9653",
"_owner": {
"_id": "5bb51a97fb250722d4f5d5e1",
"profilePhoto": "https://...",
"displayName": "displayname"
},
"createdAt": 1538648478544,
"body": "Another comment"
},
{
"_id": "5bb5e96686f1973274c03880",
"_owner": {
"_id": "5bb51a97fb250722d4f5d5e1",
"profilePhoto": "https://...",
"displayName": "displayname"
},
"createdAt": 1538648422471,
"body": "A new comment"
}
]
我有一些工作代码,首先从聚合得到排序的注释,然后单独填充,但我希望能够通过使用聚合管道得到这个查询
当前的解决方案如下所示:
const postComments = await Post.aggregate([
{ $match: { _id: mongoose.Types.ObjectId(postId) } },
{ $unwind: '$comments' },
{ $limit: 50 },
{ $skip: 50 * page },
{ $sort: { 'comments.createdAt': -1 } },
{$replaceRoot: {newRoot: '$comments'}},
{
$project: {
_owner: 1,
createdAt: 1,
body: 1
}
}
]);
await Post.populate(postComments, {path: 'comments._owner', select: 'profilePhoto displayName' } )
你可以在下面试试
const postComments = await Post.aggregate([
{ "$match": { "_id": mongoose.Types.ObjectId(postId) } },
{ "$unwind": "$comments" },
{ "$lookup": {
"from": "users",
"localField": "comments._owner",
"foreignField": "_id",
"as": "comments._owner"
}},
{ "$unwind": "$comments._owner" },
{ "$replaceRoot": { "newRoot": "$comments" }},
{ "$sort": { "createdAt": -1 } }
{ "$limit": 50 }
])