MongoDB 在对象数组中加入数据

Question

我在一个名为 diagnoses 的集合中有这样的文档:

   {
        "_id" : ObjectId("582d43d18ec3f432f3260682"),
        "patientid" : ObjectId("582aacff3894c3afd7ad4677"),
        "doctorid" : ObjectId("582a80c93894c3afd7ad4675"),
        "medicalcondition" : "high fever, cough, runny nose.",
        "diagnosis" : "Viral Flu",
        "addmissiondate" : "2016-01-12",
        "dischargedate" : "2016-01-16",
        "bhtno" : "125",
        "prescription" : [ 
            {
                "drug" : ObjectId("58345e0e996d340bd8126149"),
                "instructions" : "Take 2 daily, after meals."
            }, 
            {
                "drug" : ObjectId("5836bc0b291918eb42966320"),
                "instructions" : "Take 1 daily, after meals."
            }
        ]
    }

处方对象数组中的 drug id 来自一个名为 drugs 的单独集合，请参见下面的示例文档:

{
    "_id" : ObjectId("58345e0e996d340bd8126149"),
    "genericname" : "Paracetamol Tab 500mg",
    "type" : "X",
    "isbrand" : false
}

我正在尝试使用 native node.js 驱动程序创建一个 mongodb 查询以获得如下结果:

        {
                "_id" : ObjectId("582d43d18ec3f432f3260682"),
                "patientid" : ObjectId("582aacff3894c3afd7ad4677"),
                "doctorid" : ObjectId("582a80c93894c3afd7ad4675"),
                "medicalcondition" : "high fever, cough, runny nose.",
                "diagnosis" : "Viral Flu",
                "addmissiondate" : "2016-01-12",
                "dischargedate" : "2016-01-16",
                "bhtno" : "125",
                "prescription" : [ 
                    {
                        "drug" : 
                        {
                          "_id" : ObjectId("58345e0e996d340bd8126149"),
                          "genericname" : "Paracetamol Tab 500mg",
                          "type" : "X",
                          "isbrand" : false
                        },
                        "instructions" : "Take 2 daily, after meals."
                    },
                    ...
                ]
            }

非常感谢任何有关如何处理类似结果的建议，谢谢。

Answer 1

使用 MongoDB 3.4.4 及更新版本

使用聚合框架， $lookup 运算符支持数组

db.diagnoses.aggregate([
    { "$addFields": { 
        "prescription": { "$ifNull" : [ "$prescription", [ ] ] }    
    } },
    { "$lookup": {
        "from": "drugs",
        "localField": "prescription.drug",
        "foreignField": "_id",
        "as": "drugs"
    } },
    { "$addFields": {
        "prescription": {
            "$map": {
                "input": "$prescription",
                "in": {
                    "$mergeObjects": [
                        "$$this",
                        { "drug": {
                            "$arrayElemAt": [
                                "$drugs",
                                { 
                                    "$indexOfArray": [
                                        "$drugs._id",
                                        "$$this.drug"
                                    ] 
                                }
                            ]
                        } }
                    ]
                }
            }
        }
    } },
    { "$project": { "drugs": 0 } }
])

对于较旧的 MongoDB 版本:

您可以创建一个管道，首先使用 $unwind 将 prescription 数组展平。 运算符和一个 $lookup 后续管道步骤对“drugs”集合执行“左外连接”。申请另一个 $unwind 对从“joined”字段创建的数组进行操作。 $group 来自第一个管道的先前扁平化文档，其中 $unwind 运算符为处方数组中的每个元素输出一个文档。

组装上述管道，运行以下聚合操作:

db.diagnoses.aggregate([
    { 
        "$project": {               
            "patientid": 1,
            "doctorid": 1,
            "medicalcondition": 1,
            "diagnosis": 1,
            "addmissiondate": 1,
            "dischargedate": 1,
            "bhtno": 1,
            "prescription": { "$ifNull" : [ "$prescription", [ ] ] } 
        }
    },
    {
       "$unwind": {
           "path": "$prescription",
           "preserveNullAndEmptyArrays": true
        }
    },      
    {
        "$lookup": {
            "from": "drugs",
            "localField": "prescription.drug",
            "foreignField": "_id",
            "as": "prescription.drug"
        }
    },
    { "$unwind": "$prescription.drug" },
    { 
        "$group": {
            "_id": "$_id",
            "patientid" : { "$first": "$patientid" },
            "doctorid" : { "$first": "$doctorid" },
            "medicalcondition" : { "$first": "$medicalcondition" },
            "diagnosis" : { "$first": "$diagnosis" },
            "addmissiondate" : { "$first": "$addmissiondate" },
            "dischargedate" : { "$first": "$dischargedate" },
            "bhtno" : { "$first": "$bhtno" },
            "prescription" : { "$push": "$prescription" }
        }
    }
])

样本输出

{
    "_id" : ObjectId("582d43d18ec3f432f3260682"),
    "patientid" : ObjectId("582aacff3894c3afd7ad4677"),
    "doctorid" : ObjectId("582a80c93894c3afd7ad4675"),
    "medicalcondition" : "high fever, cough, runny nose.",
    "diagnosis" : "Viral Flu",
    "addmissiondate" : "2016-01-12",
    "dischargedate" : "2016-01-16",
    "bhtno" : "125",
    "prescription" : [ 
        {
            "drug" : {
                "_id" : ObjectId("58345e0e996d340bd8126149"),
                "genericname" : "Paracetamol Tab 500mg",
                "type" : "X",
                "isbrand" : false
            },
            "instructions" : "Take 2 daily, after meals."
        }, 
        {
            "drug" : {
                "_id" : ObjectId("5836bc0b291918eb42966320"),
                "genericname" : "Paracetamol Tab 100mg",
                "type" : "Y",
                "isbrand" : false
            },
            "instructions" : "Take 1 daily, after meals."
        }
    ]
}