MongoDB filter multi sub-documents

问题

I Have a document structured like this in mongo DB, and I want to filter to show only active subdocuments: active cars and active fruits.

    {
       "name":"Andre",
       "fruits":[
           {
              "active":true,
              "fruitname":"apple" 
           },{
              "active":false,
              "fruitname":"banana" 
           }
       ],
       "cars":[
           {
               "active":false,
               "carname":"ford"
           },{
               "active":true,
               "carname":"GM"
           },
       ]
    }

this is my desired result.

    {
       "name":"Andre",
       "fruits":[
           {
              "active":true,
              "fruitname":"apple" 
           }
       ],
       "cars":[
          {
               "active":true,
               "carname":"GM"
           },
       ]
    }

I've tried Aggregate but when any cars or any fruits active, it's return nothing.

    m_object.aggregate([
        { $match : {
           "name": "andre"
       }},
       { $unwind : "$fruits" },
       { $unwind : "$cars" },
       { $match : {
        'fruits.active':{$eq: true}
        }},
       { $match : {
        'cars.active':{$eq: true}
        }},

    { $group : {
       "name": "$name",
       cars: { $addToSet : "$cars" }
       fruits: { $addToSet : "$fruits" }
    }}
    ], function (err, result) {
        if (err) {
            console.log(err);
            return;
        }
        console.log('result');
    });

Is there any way to omit the "active":false subdocuments in those subdocuments?

回答1:

Use the following aggregation pipeline to get the desired result:

var pipeline = [
    {
        "$match": {
            "name": "Andre",
            "fruits.active": true,
            "cars.active": true
        }
    },
    { "$unwind": "$fruits" },
    { "$unwind": "$cars" },
    {
        "$match": {            
            "fruits.active": true,
            "cars.active": true
        }
    },
    { 
        "$group": {
            "_id": {
                "_id": "$_id",
                "name": "$name"
            },
            "cars": { "$addToSet" : "$cars" },
            "fruits": { "$addToSet" : "$fruits" }
        }
    },
    {
        "$project": {
            "_id": 0,
            "name": "$_id.name",
            "cars": 1,
            "fruits": 1
        }
    }    
]

m_object.aggregate(pipeline)
        .exec(function (err, result) {
            if (err) {
                console.log(err);
                return;
            }
            console.log('result');
        });

Or you can use the aggregation pipeline builder as follows:

m_object.aggregate()
        .match({
            "name": "Andre",
            "fruits.active": true,
            "cars.active": true
         })
        .unwind("fruits")
        .unwind("cars")
        .match({
            "fruits.active": true,
            "cars.active": true
         })
        .group({
            "_id": {
                "_id": "$_id",
                "name": "$name"
            },
            "cars": { "$addToSet" : "$cars" },
            "fruits": { "$addToSet" : "$fruits" }
        })
        .project({
            "_id": 0,
            "name": "$_id.name",
            "cars": 1,
            "fruits": 1
        })
        .exec(callback);

来源：https://stackoverflow.com/questions/30198116/mongodb-filter-multi-sub-documents