Question

请原谅标题。可以找到更好的描述我想做什么。

我有一组存储以下信息的消息

code：消息的唯一标识码
from：来自
to：邮件发送到的电话号码
消息：消息文本
读数：一个ObjectIds数组。 ids引用另一个集合中的文档名称“users”。如果ObjectId在这里意味着该消息已被该特定用户读取。

示例数据

{
    "_id" : ObjectId("59ba30c95869d32a803e4c4d"),
    "code" : "SM54c9366e9b8544e89bdcf2ee841adea7",
    "from" : "+49157xxxxxxx",
    "to" : "+49160xxxxxxxx",
    "message" : "xxxxxxxx",
    "createdAt" : ISODate("2017-09-14T07:33:39.000Z"),
    "lastModifiedAt" : ISODate("2017-09-14T07:33:32.324Z"),
    "status" : "delivered",
    "room" : ObjectId("59bfa293bd7717251cecfae7"),
    "readings" : [ 
        ObjectId("59c25751dcfdaf2944ee2fae"), 
        ObjectId("59c25751dcfdaf2944e32fae")
    ],
}

/* 2 */
{
    "_id" : ObjectId("59ba3270f53b7f2fb4fa807f"),
    "code" : "SM04585672d02644018e3ff466d73c571d",
    "from" : "+49xxxxxxx",
    "to" : "+49xxxxxxxx",
    "message" : "xxxxxxx",
    "createdAt" : ISODate("2017-09-14T07:40:42.000Z"),
    "lastModifiedAt" : ISODate("2017-09-14T07:40:34.338Z"),
    "status" : "delivered",
    "room" : ObjectId("59bfa293bd7717251cecfae7"),
    "readings" : [ 
        ObjectId("59c25751dcfdaf2944ee2fae")
    ],
}

我希望实现的是，如果特定用户已阅读该消息，则消息会获得额外的字段“hasRead”。

这是我想要实现的结果

{
    "_id" : ObjectId("59ba30c95869d32a803e4c4d"),
    "code" : "SM54c9366e9b8544e89bdcf2ee841adea7",
    "to" : "+491606983534",
    "message" : "Schau mer mal",
    "createdAt" : ISODate("2017-09-14T07:33:39.000Z"),
    "lastModifiedAt" : ISODate("2017-09-14T07:33:32.324Z"),
    "status" : "delivered",
    "room" : ObjectId("59bfa293bd7717251cecfae7"),
    "hasRead" : true
}

/* 2 */
{
    "_id" : ObjectId("59ba3270f53b7f2fb4fa807f"),
    "code" : "SM04585672d02644018e3ff466d73c571d",
    "to" : "+491606983534",
    "message" : "Schau mer mal",
    "createdAt" : ISODate("2017-09-14T07:40:42.000Z"),
    "lastModifiedAt" : ISODate("2017-09-14T07:40:34.338Z"),
    "status" : "delivered",
    "room" : ObjectId("59bfa293bd7717251cecfae7"),
    "hasRead" : true
}

我构建了一个具有以下阶段的聚合，但它对于这么简单的任务看起来很大，我想知道是否有更优雅，更轻松的方法呢？

阶段是：

$ addFields：检查读数数组是否为0.如果为0则添加虚拟ObjectId，否则设置读数数组
$ unwind：展开读数数组
$ addFields：在检查特定ObjectId是否与“读数”字段匹配时添加字段“hasRead”。如果等于其他则为真
$ group：除“hasRead”字段外的所有字段分组，“hasRead”基于$ max hasRead
$ project：构造结果以使其成为扁平对象。

这是我的代码：

db.getCollection('sms').aggregate([
{ $addFields: {
    "readings": {
        "$cond": {
            if: { $or: [ { "$gt": [ {"$size": "$readings"},0] } ]} ,
            then: "$readings",
            else: [ObjectId("000000000000000000000000")]
        }
    }
}},
{ $unwind: "$readings" },
{ $addFields: { 
    "hasRead": { 
        $cond: { 
            if: { 
                $eq: ["$readings", ObjectId("59c25751dcfdaf2944ee2fae")] 
            }, 
            then: true, 
            else: false 
        }
    } 
  } 
},
{ $group: {
    _id: { 
        _id: "$_id",
        code: "$code",
        from: "$from",
        to: "$to",
        message: "$message",
        createdAt: "$createdAt",
        lastModifiedAt: "$lastModifiedAt",
        room: "$room"
    },
    hasRead: { $max: "$hasRead" }
}},

{ $project: {
    "_id": "$_id._id",
    "code": "$_id.code",
    "from": "$_id.from",
    "to": "$_id.to",
    "message": "$_id.message",
    "createdAt": "$_id.createdAt",
    "lastModifiedAt": "$_id.lastModifiedAt",
    "room": "$_id.room",
    "hasRead": "$hasRead"
}}
])

在浏览完答案后，Neil（见评论）给了另一个问题，可能会对此提出疑问：

db.getCollection('sms').aggregate([
    { "$addFields": {
        "hasRead" : {
            "$filter": {
                "input": { "$setUnion": [ "$readings", []] },
                "as": "o",
                "cond" : {
                    "$eq": [ "$$o",ObjectId("59c25751dcfdaf2944ee2fae")]
                    }
                }
            }
        }
    },
    { "$project": {
        "_id": 1,
        "code": 1,
        "to": 1,
        "message": 1,
        "createdAt": 1,
        "lastModifiedAt" : 1,
        "status": 1,
        "room": 1,
        "hasRead": { 
            "$cond": {
            if: { $or: [ { "$gt": [ {"$size": "$readings"},0] } ]} ,
            then: true,
            else: false
            }
        }
    }
}
])

基于数组

0 个答案: