javascript - 无法 "skip" Mongoose 子文档

Question

我正在使用 Mongoose 和 Node ，我正在尝试对子文档中的数据进行分页。我可以限制子文档，但不能跳过它们。

我使用的版本是:

蒙戈3.0.0

Node 0.10.33

Mongoose 3.9.7

数据

[{ 
    "name" : "Ranger Table", 
    "_id" : ObjectId("550234d3d06039d507d238d8"),
    "body" : [ 
        { 
            "name" : "Jason", 
            "colour" : "Red", 
            "animal" : "T-rex", 
            "_id" : ObjectId("550234d3d06039d507d238de") 
        }, 
        { 
            "name" : "Billy", 
            "colour" : "Blue", 
            "animal" : "Triceratops", 
            "_id" : ObjectId("550234d3d06039d507d238dd") 
        }, 
        { 
            "name" : "Zach", 
            "colour" : "Black", 
            "animal" : "Mastadon", 
            "_id" : ObjectId("550234d3d06039d507d238dc") 

        },
        {
            "name" : "Tommy",
            "colour" : "Green",
            "animal" : "Dragon"
            "_id" : ObjectId("550234d3d06039d507d238d9") 
        }   
    ]
},{ 
    "name" : "Bot Table", 
    "_id" : ObjectId("5502d205184cd74033f64e6b"),
    "body" : [ 
        { 
            "name" : "Optimus", 
            "team" : "Autobots", 
            "class" : "Leader", 
            "_id" : ObjectId("550234d3d06039d507d238d9") 
        }, 
        { 
            "name" : "Bumblebee", 
            "team" : "Autobots", 
            "class" : "Scout", 
            "_id" : ObjectId("550234d3d06039d507d238da") 
        }, 
        { 
            "name" : "Astrotrain", 
            "team" : "Decepticons", 
            "class" : "Transport", 
            "_id" : ObjectId("550234d3d06039d507d238db") 

        }
    ]
}]

代码

var BodySchema = new Schema({random: String},{strict:false});

var FeedSchema = new Schema({
  name: String,
  body:[BodySchema]
});

var feed = mongoose.model('Feed', FeedSchema);

feed.find({_id:'550234d3d06039d507d238d8'})
    .populate({
        "path":"body",
        "options":{
            limit:2, //This works fine
            skip:2  //This doesn't work
        }
    })
    .exec(function(err, result){

        if(err){return(res.send(500, err))}

        res.send(result);
    });

结果上面的代码确实将“body”子文档的数量限制为 2，但不跳过任何子文档。

上面的代码返回:

{ 
    "name" : "Ranger Table", 
    "_id" : ObjectId("550234d3d06039d507d238d8"),
    "body" : [ 
        { 
            "name" : "Jason", 
            "colour" : "Red", 
            "animal" : "T-rex", 
            "_id" : ObjectId("550234d3d06039d507d238de") 
        }, 
        { 
            "name" : "Billy", 
            "colour" : "Blue", 
            "animal" : "Triceratops", 
            "_id" : ObjectId("550234d3d06039d507d238dd") 
        }
    ]
} 

但它应该返回这个:

{ 
    "name" : "Ranger Table", 
    "_id" : ObjectId("550234d3d06039d507d238d8"),
    "body" : [ 
        { 
            "name" : "Zach", 
            "colour" : "Black", 
            "animal" : "Mastadon", 
            "_id" : ObjectId("550234d3d06039d507d238dc") 

        },
        {
            "name" : "Tommy",
            "colour" : "Green",
            "animal" : "Dragon"
            "_id" : ObjectId("550234d3d06039d507d238d9") 
        }
    ]
} 

Answer 1

我找到的解决方案是使用聚合并使用 $unwind 指定子文档的名称。

http://docs.mongodb.org/manual/reference/operator/aggregation/

feed.aggregate([
    {'$match':{_id:id('550234d3d06039d507d238d8')}},
    {'$unwind':'$body'},
    {'$skip':2},
    {'$limit':2},
], function(err, result){

    if(err){return(res.send(500, err))}

    res.send(result);

});