猫鼬聚合查找管道不起作用

Question

知道为什么此聚合仅匹配 post，但不填充评论吗？

我需要来自评论集合的用户评论，但只有空管道 returns 条评论

Post.aggregate(...)

[
        {
            "$match": {
                "author": ObjectId(...)
            }
        },
        {
            "$lookup": {
                "from": "comments",
                "let": {
                    "postID": "$post",
                    "isHiden": "$isHiden"
                },
                "pipeline": [
                    {
                        "$match": {
                            "$expr": {
                                "$and": [
                                    {
                                        "$eq": [
                                            "$_id",
                                            "$$postID"
                                        ]
                                    },
                                    {
                                        "$eq": [
                                            "$$isHiden",
                                            0
                                        ]
                                    }
                                ]
                            }
                        }
                    }
                ],
                "as": "comments"
            }
        }
    ]

评论对象包含

{
  "_id": "5f7de8491af5c0e246d42609",
  "isHiden": false,
  "text": "...",
  "post": "5f7de8491af5c0e246d42605"
}

Post型号为

{
  "_id": "5f7de8491af5c0e246d42605",
  "title": "Corporate Web Coordinator",
  "body": "...",
  "author": "5f7de8491af5c0e246d42602"
  }
}

我想得到这样的结果：

       {
            "_id": "5f7de8491af5c0e246d42605",
            "confirm_status": "pending",
            "title": "Dynamic Marketing Supervisor",
            "body": "...",
            "author": "5f7de8491af5c0e246d42604",
            "comments": [
                  { "_id": "5f7de8491af5c0e246d42609",
                    "isHiden": false,
                    "text": "...",
                    "post": "5f7de8491af5c0e246d42605" }
             ]
        }

我尝试了所有方法，但没有任何效果...

我会很感激任何帮助

Answer 1

问题出在您的查询中，

post 字段出现在注释 table 中并且您使用了 _id，因此它应该是 $post,
内部管道字段 isHiden 不存在于 post table 中并且您在 let 中定义该字段，它应该是，

    $lookup: {
      from: "comments",
      let: { postID: "$_id" },
      pipeline: [
        {
          $match: {
            $expr: [
              {
                $eq: [
                  "$$postID",
                  "$post"
                ]
              }
            ],
            isHiden: false
          }
        }
      ],
      as: "comments"
    }

Playground

猫鼬聚合查找管道不起作用

Mongoose aggregation lookup pipeline doesn't work

javascript

mongoose

mongodb

node.js

mongoose-populate