android - mongodb过滤与数组中objectid关联的内容状态

Question

我想通过过滤功能导入数据。

我认为我们应该使用“聚合”而不是“查找”。

The conditions for the data I want are:

1. There is A Collection and B Collection.

2. The 'contents' of A Collection points to the "_id" of B Collection.

3. The corresponding value is only fetched when the "Visibility" value of the B Collection is "true".

“A”系列:

{
   "_id" : ObjectId("aaaaa"),
    "title" : "study list",   
    "contents" : [ ObjectId("11111"), ObjectId("22222") ]
}
{
   "_id" : ObjectId("bbbbb"),
    "title" : "study list",   
    "contents" : [ ObjectId("33333"), ObjectId("44444") ]
}
{
   "_id" : ObjectId("ccccc"),
    "title" : "study list",   
    "contents" : [ ObjectId("55555") ]
}

“B”系列:

{
   "_id" : ObjectId("11111"),
    "visibility" : true
}
{
   "_id" : ObjectId("22222"),
    "visibility" : true
}
{
   "_id" : ObjectId("33333"),
    "visibility" : true
}
{
   "_id" : ObjectId("44444"),
    "visibility" : false
}
{
   "_id" : ObjectId("55555"),
    "visibility" : false
}

==数据结果

{
   "_id" : ObjectId("aaaaa"),
    "title" : "study list",   
    "contents" : [ ObjectId("11111"), ObjectId("22222") ]
}

如何获取我想要的数据？

Answer 1

您可以使用以下聚合

db.collectionA.aggregate([
  { "$lookup": {
    "from": "collectionB",
    "localField": "contents",
    "foreignField": "_id",
    "as": "data"
  }},
  { "$match": {
    "data": {
      "$not": {
        "$elemMatch": { "visibility": false }
      }
    }
  }}
])