通过

$bucket

聚合管道中的 $bucket 阶段根据指定的边界将输入文档分组到存储桶中。 这对于创建直方图或将数据分类到范围尤其有用。 它允许你定义自定义存储桶边界，并提供一种方法来汇总这些范围内的数据。

语法

{
  $bucket: {
    groupBy: <expression>,
    boundaries: [ <lowerBoundary>, <upperBoundary>, ... ],
    default: <defaultBucket>,
    output: {
      <outputField1>: { <accumulator1> },
      ...
    }
  }
}

参数

参数 DESCRIPTION
groupBy 文档分组所依据的表达式。
boundaries 用于定义存储桶的边界值的数组。 数组必须按升序排序，并至少包含两个值。
default 用于不在指定边界内的文档的存储桶名称。
output 用于为每个存储桶指定计算字段的可选字段。

例子

请考虑商店集合中的这个示例文档。

{
    "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
    "name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
    "location": {
        "lat": -89.2384,
        "lon": -46.4012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "promotionEvents": [
        {
            "eventName": "Unbeatable Bargain Bash",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 23
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 7,
                    "Day": 2
                }
            },
            "discounts": [
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 7
                },
                {
                    "categoryName": "Bitters",
                    "discountPercentage": 15
                },
                {
                    "categoryName": "Brandy",
                    "discountPercentage": 8
                },
                {
                    "categoryName": "Sports Drinks",
                    "discountPercentage": 22
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 19
                }
            ]
        },
        {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    ]
}

示例 1：将 fullSales 划分到范围内

此查询将 fullSales 字段分类为三个存储桶： [0, 1000)， [1000, 5000)以及 [5000, 10000)。 不属于这些范围的文档将分组到默认存储桶中。

db.stores.aggregate([
  {
    $bucket: {
      groupBy: "$sales.fullSales",
      boundaries: [0, 1000, 5000, 10000],
      default: "Other",
      output: {
        count: { $sum: 1 },
        totalSales: { $sum: "$sales.fullSales" }
      }
    }
  }
])

此查询返回以下结果：

[
  { "_id": 1000, "count": 1, "totalSales": 3700 },
  { "_id": "Other", "count": 41504, "totalSales": 0 }
]

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