如何在 mongodb 中使用查找来匹配数组字段？

Question

我有两个集合，一个用于存储菜单详细信息，另一个用于存储项目详细信息 以下是“allmenu”集合。

{
    "_id" : ObjectId("5ce7454f77af2d1143f84c38"),
    "menu_name" : "mainmenu1",
    "sub_menus" : [ 
        "submenu1",
        "submenu2"
    ]
}

以下是“项目”集合。

{
    "_id" : ObjectId("5cda19d2e7bb82e771931adb"),
    "project_name" : "p1",
    "sub_menus" : "submenu1",

}
{
    "_id" : ObjectId("5cda19d2e7bb82e771931adb"),
    "project_name" : "p2",
    "sub_menus" : "submenu2",

}

我想要下面的结果

  {
    "_id" : ObjectId("5ce7454f77af2d1143f84c35"),
    "menu_name" : "mainmenu1",
    "sub_menus" : [
      {"sub_menu_name" : "submenu1",
       "projectData" : [ 
        {
            "project_name" : "p1",            
        }
       ]
      }
    ]  
}

我尝试了以下查询

db.getCollection('allmenu').aggregate([
{"$unwind":"$sub_menus"},
{"$lookup":{
        "from" :"project",
        "localField":"sub_menus",
        "foreignField":"sub_menus",
        "as":"newData"
        }
}])

我检查了所有与数组查找相关的问题。但所有的问题都与此不同。

Answer 1

你可以使用下面的聚合

db.collection.aggregate([
  { "$lookup": {
    "from": "project",
    "let": { "sub_menus": "$sub_menus" },
    "pipeline": [
      { "$match": { "$expr": { "$in": ["$sub_menus", "$$sub_menus"] }}},
      { "$project": {
        "projectData": [{ "project_name": "$project_name" }],
        "sub_menu_name": "$sub_menus"
      }}
    ],
    "as": "sub_menus"
  }}
])

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