异常的Mongo DB查询

Question

I need to do a special query. I have got an list of items availiable to do some Production. With this data I need to query the Documents where each type of item is in the List. A few (slightly) simplyfied Document looks may like this.

{

    "productname": "iron",
    "requirements": [
        {
            "ammount": 2,
            "item": "coal"
        },
        {
            "ammount": 2,
            "item": "ironore"
        }
    ],
}

{

    "productname": "coal",
    "requirements": [
        {
            "ammount": 2,
            "item": "wood"
        }
    ],
}

{

    "productname": "copper",
    "requirements": [
        {
            "ammount": 2,
            "item": "coal"
        },
        {
            "ammount": 2,
            "item": "copperore"
        }
    ],
}

{

    "productname": "Chair",
    "requirements": [
        {
            "ammount": 2,
            "item": "wood"
        },
        {
            "ammount": 2,
            "item": "nails"
        },
        {
            "ammount": 2,
            "item": "paint"
        }
    ],
}
{

    "productname": "Wooden Toy",
    "requirements": [
        {
            "ammount": 2,
            "item": "wood"
        },
        {
            "ammount": 2,
            "item": "paint"
        }
    ],
}

An example list may look like: ["wood", "beer","coal", "paint", "copperore"]

This should return the Documents of "Coal", "Copper" and "Wooden Toy", thus all of their requirements are in the List. For "Chair" the "nails" are missing and for "Iron" the "Ironore" is missing.

(Sorry for my bad english ;) )

Answer 1

From your given documents, if you want to find the document that contains requirements with coal and coppercore then the following query:

> db.materials.find({"requirements.item" : "coal", "requirements.item": "copperore" }).pretty()

Would return:

{
        "_id" : ObjectId("584990f083842cff8826d44f"),
        "productname" : "copper",
        "requirements" : [
                {
                        "ammount" : 2,
                        "item" : "coal"
                },
                {
                        "ammount" : 2,
                        "item" : "copperore"
                }
        ]
}

Answer 2

如果我正确理解了您的问题（不确定是否可以这样做），则可以使用all运算符：

db.materials.find({"requirements.item": {$all: ["coal", "copperore"]}})

Answer 3

You can do this with $redact and $setIsSubset as a $cond tion

var myList =  ["wood", "beer","coal", "paint", "copperore"]
db.collection.aggregate([
    { "$match": { "requirements.item": { "$in":  myList } } },
    { "$redact": { 
        "$cond": [ 
            { 
                "$setIsSubset": [ 
                    "$requirements.item", 
                    myList 
                ] 
            }, 
            "$$KEEP", 
            "$$PRUNE"
       ]
    }}
])