如何避免 MongoDB 聚合中的 $unwind 和 $group

Question

我在 MongoDB 有 collection 个“马酒店”。我需要创建一个查询：

• 10 月 23 日至 24 日有售
• 至少可容纳 2 人

我已经成功创建了一个使用 $unwind 和 $group（以及更多）工作的聚合管道，但查询似乎不必要地臃肿和复杂。可以用更好的方式创建它吗？

collection中的文档（旅馆）示例：

{
  "_id": {
    "$oid": "616c18d09542c9e6882a7dce"
  },
  "userId": {
    "$oid": "61247e2f8cc1782a4f6762fe"
  },
  "active": true,
  "status": "approved",
  "title": "Test hotel 10",
  "description": "Lorem ipsum dolor sit amet",
  "rooms": [
    {
      "type": "house",
      "isShared": false,
      "isHorseRoom": false,
      "spots": 4,
      "dayPrice": 150,
      "includedSpots": 2,
      "extraSpotDayPrice": 30,
      "reservations": [
        {
          "reservationId": "someReservationId",
          "fromDate": {
            "$date": "2021-10-23T00:00:00Z"
          },
          "toDate": {
            "$date": "2021-10-24T00:00:00Z"
          },
          "spots": 3
        },
        {
          "fromDate": {
            "$date": "2021-10-16T00:00:00Z"
          },
          "toDate": {
            "$date": "2021-10-17T00:00:00Z"
          },
          "spots": 1,
          "reservationId": "someReservationId"
        }
      ]
    },
    {
      "type": "hayloft",
      "isShared": true,
      "isHorseRoom": false,
      "spots": 10,
      "dayPrice": 40,
      "includedSpots": 1,
      "extraSpotDayPrice": 40
    },
    {
      "type": "grass",
      "isShared": false,
      "isHorseRoom": true,
      "spots": 4,
      "dayPrice": 50,
      "reservations": [
        {
          "reservationId": "someReservationId",
          "fromDate": {
            "$date": "2021-10-30T00:00:00Z"
          },
          "toDate": {
            "$date": "2021-10-31T00:00:00Z"
          },
          "spots": 2
        },
        {
          "reservationId": "someReservationId",
          "fromDate": {
            "$date": "2021-11-06T00:00:00Z"
          },
          "toDate": {
            "$date": "2021-11-07T00:00:00Z"
          },
          "spots": 2
        }
      ]
    },
    {
      "type": "grass",
      "isShared": false,
      "isHorseRoom": true,
      "spots": 2,
      "dayPrice": 100
    },
    {
      "type": "box",
      "isShared": false,
      "isHorseRoom": true,
      "spots": 1,
      "dayPrice": 80
    },
    {
      "type": "box",
      "isShared": false,
      "isHorseRoom": true,
      "spots": 1,
      "dayPrice": 80
    }
  ],
  "weekDiscountPercentage": 0.2,
  "priceChanges": [
    {
      "fromDate": {
        "$date": "2021-07-01T00:00:00Z"
      },
      "toDate": {
        "$date": "2021-07-31T00:00:00Z"
      },
      "percentage": 1.2
    }
  ]
}

我当前的工作查询[=​​29=]

[
  // Stage 1: Only keep active and approved hotels
  {
    $match: {
      status: "approved",
      active: true,
    },
  },
  // Stage 2: Filter the 'rooms' to only keep rooms which is either: 
  // a) shared, b) has no reservations or c) is not shared and has a reservation in that time frame.
  {
    $addFields: {
      rooms: {
        $filter: {
          input: "$rooms",
          as: "room",
          cond: {
            $or: [
              {
                $eq: ["$$room.isShared", true],
              },
              {
                $eq: ["$$room.reservations", []],
              },
              {
                $not: ["$$room.reservations"],
              },
              {
                $and: [
                  {
                    $eq: ["$$room.isShared", false],
                  },
                  {
                    $eq: [
                      {
                        $filter: {
                          input: "$$room.reservations",
                          as: "reservation",
                          cond: {
                            $and: [
                              {
                                $gte: [
                                  "$$reservation.fromDate",
                                  ISODate("2021-10-23"),
                                ],
                              },
                              {
                                $lt: [
                                  "$$reservation.fromDate",
                                  ISODate("2021-10-24"),
                                ],
                              },
                            ],
                          },
                        },
                      },
                      [],
                    ],
                  },
                ],
              },
            ],
          },
        },
      },
    },
  },
  // Stage 3: Unwind rooms
  {
    $unwind: {
      path: "$rooms",
    },
  },
  // Stage 4: We know all these rooms are either shared and/or available
  // This calculates how many spots are reserved within the date range
  {
    $project: {
      spots: "$rooms.spots",
      _id: "$_id",
      type: "$rooms.type",
      title: "$title",
      dayPrice: "$rooms.dayPrice",
      isShared: "$rooms.isShared",
      reserved: {
        $sum: {
          $map: {
            input: "$rooms.reservations",
            as: "item",
            in: {
              $cond: [
                {
                  $and: [
                    {
                      $gte: [
                        "$$item.fromDate",
                        ISODate("2021-10-23"),
                      ],
                    },
                    {
                      $lte: [
                        "$$item.fromDate",
                        ISODate("2021-10-24"),
                      ],
                    },
                  ],
                },
                "$$item.spots",
                0,
              ],
            },
          },
        },
      },
    },
  },
  // Stage 5: Add a new field containing the number of spots left available in the time frame for each room
  {
    $addFields: {
      free: {
        $subtract: ["$spots", "$reserved"],
      },
    },
  },
  // Stage 6: Group the unwinded documents together again by the hotel id
  // and calculate the total available spots
  {
    $group: {
      _id: "$_id",
      title: { $first: "$title" },
      rooms: {
        $push: {
          name: "$_id.actName",
          spots: "$spots",
          dayPrice: "$dayPrice",
          reserved: "$reserved",
          type: "$type",
          free: "$free",
        },
      },
      freecount: { $sum: "$free" },
    },
  },
  // Stage 7: Only keep the hotels which have e.g. minimum 2 free spots left (depending on user input)
  {
    $match: {
      freecount: { $gte: 2 },
    },
  },
];

Answer 1

好的，我使用 addFields 阶段和 $sum 和两个 $map 阶段创建了一个解决方案。

这是我的新 addFields 阶段，它取代了上面的阶段 2、3、4、5 和 6。

{
  reservedSpots: {
    "$sum": {
      "$map": {
        "input": "$rooms",
        "as": "room",
        "in": {

          "$sum": {
            "$map": {
              "input": "$$room.reservations",
              "as": "reservation",
              "in": {
                "$cond": [
                  // Check if the reservation dates matches
                  { 
                    "$and": [
                      { "$gte": ["$$reservation.fromDate", ISODate('2021-10-22')] }, 
                      { "$lte": ["$$reservation.toDate", ISODate('2021-10-25')] }
                    ]
                  }, 
                  // If yes, then
                  {
                    $cond: [
                      // Check if the room is shared
                      { $eq: ["$$room.isShared", false] },
                      // If yes, then add all spots of the room
                      "$$room.spots",
                      // If no, only add the spots of the reservation
                      "$$reservation.spots"
                    ]
                  },
                  // If no, don't add to $sum
                  0
                ]
              }
            }
          }
          
        }
      }
    }
  }
}