Mongodb查询:每个项目的日期最新记录 [英] Mongodb Query: Latest record by date for each item

问题描述

一个集合中有六个设备，每个设备都有很多记录，一些记录着新的日期，有些记录则有一个星期或一个月的历史.我需要一个查询，该查询返回每个设备的最新最近记录.对于.aggregate()，我需要提交完整的数据".

There are six devices in a collection, each has many records, some have records of new dates and some have week or/and month older. I need a query which returns latest last record of each device. In the case of .aggregate() I need that complete "data" filed.

这是示例json.

{
"date_time" : some-date
"device_id" : 27,
"gateway_id" : 1,
"data": [{"r" : 203,"v" : 3642},{"r" : 221,"v" : 3666}]
}
{
"date_time" : some-date
"device_id" : 28,
"gateway_id" : 1,
"data": [{"r" : 203,"v" : 3002},{"r" : 221,"v" : 3006}]
}
{
"date_time" : some-date
"device_id" : 29,
"gateway_id" : 1,
"data": [{"r" : 203,"v" : 3002}, {"r" : 221,"v" : 3006}]
}

我尝试了很多查询，但没有成功.

I tried a lot of queries but no success.

在这种情况下，请注意以下事项.

Please not the following are not for this case.

db.col.find({"device_id": {"$in": devices}, "date_time": { "$gte": last_date}}) .sort({$natural: -1})

db.col.find({"device_id": {"$in": devices}, "date_time": { "$gte": last_date}}) .sort({$natural: -1}).limit(1)

db.col.find({"device_id": {"$in": devices}}) .sort({"date_time": -1}).limit(1)

db.col.find({"device_id": {"$in": devices}}) .sort({"_id": -1}).limit(1)

我正在寻找仅提供集合中每个设备的最新记录的查询.请注意，对于.aggregate()，我需要提交完整的数据".

I am looking for the query which provides only latest record of every device in collection. Please note that in the case of .aggregate() I need that complete "data" filed.

推荐答案

尝试以下代码段

db.collection.aggregate([
            {$group: {
                    "_id": "$device_id",
                    "gateway_id": {"$last":"$gateway_id"},
                     data: {$last: '$data'},
                     date: {$last: '$date_time'},
                }},
            {$project: {
                     "device_id": "$_id",
                      "gateway_id": "$gateway_id",
                      "data": "$data",
                      "date_time": "$date"
                  }},
            {$sort: {
                    'date': -1
                }}
        ])

在上面的查询组中，按设备ID和日期，每一行中的数据和gateway_id将是最新的.

In above query group by device id and date, data, and gateway_id will be latest in each row.

输出为-

{
    "result" : [ 
        {
            "_id" : 29,
            "gateway_id" : 1,
            "data" : [ 
                {
                    "r" : 203,
                    "v" : 3002
                }, 
                {
                    "r" : 221,
                    "v" : 3006
                }
            ],
            "device_id" : 29,
            "date_time" : "a"
        }, 
        {
            "_id" : 28,
            "gateway_id" : 1,
            "data" : [ 
                {
                    "r" : 203,
                    "v" : 3002
                }, 
                {
                    "r" : 221,
                    "v" : 3006
                }
            ],
            "device_id" : 28,
            "date_time" : "b"
        }, 
        {
            "_id" : 27,
            "gateway_id" : 1,
            "data" : [ 
                {
                    "r" : 203,
                    "v" : 3642
                }, 
                {
                    "r" : 221,
                    "v" : 3666
                }
            ],
            "device_id" : 27,
            "date_time" : "a"
        }
    ],
    "ok" : 1
}

谢谢

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