pymongo：如何从 mongodb 的字段中获取多个结果？

Question

我想用 python3 pymongo 获取由 'name' 创建的 'data' 项目中的每个 'ecg_raw'。

如果我知道 'name' 和 'time_info'，我如何获得 4 个 ecg_raw 数据 which time_info == '2018-09-01 00:00:03'

我想获取每个 ecg_raw 数据，例如 [[8,2],[1,10],[9,4],[1,9]]

我试过了

db.g.find({"data":{"$elemMatch":{"time_info":"2018-09-01 00:00:03"}}},{"name":1,"data":{"$elemMatch":{"time_info":"2018-09-01 00:00:03"}}})

但它只返回一个像底部这样的值。

{'_id': ObjectId('5b90d401219e9c9f72cac8c4'), 'name': 'testDog3', 'data': [{'time_info': '2018-09-01 00:00:03', 'ecg_raw': [8, 2]}]}

请帮帮我。

> db.g.find().pretty()
{
"_id" : ObjectId("5b90d401219e9c9f72cac8c4"),
"name" : "testDog3",
"data" : [
    {
        "time_info" : "2018-09-01 00:00:03",
        "ecg_raw" : [
            8,
            2
        ]
    },
    {
        "time_info" : "2018-09-01 00:00:03",
        "ecg_raw" : [
            1,
            10
        ]
    },
    {
        "time_info" : "2018-09-01 00:00:03",
        "ecg_raw" : [
            9,
            4
        ]
    },
    {
        "time_info" : "2018-09-01 00:00:03",
        "ecg_raw" : [
            1,
            9
        ]
    },
    {
        "time_info" : "2018-09-01 00:00:04",
        "ecg_raw" : [
            10,
            6
        ]
    },
    {
        "time_info" : "2018-09-01 00:00:04",
        "ecg_raw" : [
            1,
            6
        ]
    }
]
}

Answer 1

试试这个。

聚合([{$match:{'name':'testDog3'}},{ "$unwind": "$data" },{ "$match": {"data.time_info":"2018-09 -01 00:00:03"}}])