如何过滤文档中的嵌入式文档？

Question

我正在做一个包含很多数据库操作的集成任务，并且一切顺利，直到无法过滤文档中的嵌入式文档。

我的文件看起来像

{
    flightId: "IND-101",
    AircraftName: "Delta Airlines",
    fare: 600,
    availableSeats: 5,
    status: "Running",
    bookings: [
        {
            customerId: "P1001",
            bookingId: 2001,
            noOfTickets: 3,
            bookingCost: 1800
        },
        {
            customerId: "S1001",
            bookingId: 2003,
            noOfTickets: 2,
            bookingCost: 1200
        }
    ]
},
{
    flightId: "IND-102",
    AircraftName: "JetBlue",
    fare: 750,
    availableSeats: 20,
    status: "Cancelled",
    bookings: [
        {
            customerId: "P1001",
            bookingId: 2002,
            noOfTickets: 3,
            bookingCost: 2250
        },
        {
            customerId: "G1001",
            bookingId: 2004,
            noOfTickets: 2,
            bookingCost: 1500
        }
    ]
}

我尝试了以下代码，但显然，它正在返回所有预订文件。

return flightModel.find({ $and: [{ flightId: flightId }, { "bookings.customerId": customerId }] }, { bookings:1, _id: 0 })

变量flightId和customerId使用函数给出。 如果我将flightId指定为IND-101，将customerID指定为P1001，则所需的输出为

{
        customerId: "P1001",
        bookingId: 2001,
        noOfTickets: 3,
        bookingCost: 1800
    }

那我该怎么做呢？ 如何根据过滤条件选择特定的嵌入式文档？

Answer 1

您可以运行汇总查询以$filter和$project所需的字段。 这样的事情应该起作用。

let pipeline = [
  {$match: {flightId: flightId}},
  {$filter: {
    input: '$bookings'
    as: 'booking',
    cond: {$eq: {'$$booking.customerId', customerId}}
  }},
  {$project: {
    bookings: "$bookings"
  }}
]

flightModel.aggregate(pipeline);