使用mgo查询子元素mongodb时不支持的投影选项

Question

I am working on a query to a mongodb with mgo using golang but it throws Unsupported projection option error while querying a sub document.

I am working on below document

{
    "_id" : ObjectId("5b64a0d3931653c36bcaf0b5"),
    "quantity" : 2,
    "product" : "ABC",   
    "children" : [ 
        {           
            "isBlocked" : true,
            "blockedMessage" : "Error occurred: TRACEID",
            "serialNo" : "abc123",
            "token" : "foo456",            
        }
    ]
}

The query I am using is

bson.M{"_id": 0, "children": bson.M{"serialNo": "abc123"}}

May I know where the mistake is?

Answer 1

Matching array element should be done with $elemMatch

Raw mongodb query looks like:

db.collection.find({_id: ObjectId('...'), children: {$elemMatch: {serialNo: 'abc123'}}});