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$documentNumber(聚合)

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  • 定义
  • 行为
  • 示例

版本 5.0 中的新增功能

$documentNumber

返回文档在 $setWindowFields阶段分区中的位置(称为文档编号)。

$setWindowFields 阶段 sortBy 字段决定文档编号。有关 MongoDB 如何比较不同类型字段的更多信息,请参阅 BSON 比较顺序

$documentNumber会为分区中的每个文档返回一个唯一的数字,即使多个文档在分区中具有相同的 SortBy 字段值也是如此。

$documentNumber 只能在 $setWindowFields 阶段使用。

$documentNumber 事务语法:

{ $documentNumber: { } }

$documentNumber 不接受任何参数。

$documentNumber 包括 sortBy 字段为 null 或缺失的文档。

$documentNumber$rank$denseRank 根据 sortBy 字段值返回文档的位置。

$documentNumber$rank$denseRank 的不同之处在于如何处理分区中具有相同 sortBy 字段值的文档:

  • $rank$denseRank 返回这些文档的相同位置(称为等级)。

  • $documentNumber 返回这些文档的唯一位置(称为文档编号)。

请参阅重复值、Null 和缺失值的文档编号中的示例。

创建cakeSales集合,其中包含加利福尼亚州 ( CA ) 和华盛顿州 ( WA ) 的蛋糕销售情况:

db.cakeSales.insertMany( [
{ _id: 0, type: "chocolate", orderDate: new Date("2020-05-18T14:10:30Z"),
state: "CA", price: 13, quantity: 120 },
{ _id: 1, type: "chocolate", orderDate: new Date("2021-03-20T11:30:05Z"),
state: "WA", price: 14, quantity: 140 },
{ _id: 2, type: "vanilla", orderDate: new Date("2021-01-11T06:31:15Z"),
state: "CA", price: 12, quantity: 145 },
{ _id: 3, type: "vanilla", orderDate: new Date("2020-02-08T13:13:23Z"),
state: "WA", price: 13, quantity: 104 },
{ _id: 4, type: "strawberry", orderDate: new Date("2019-05-18T16:09:01Z"),
state: "CA", price: 41, quantity: 162 },
{ _id: 5, type: "strawberry", orderDate: new Date("2019-01-08T06:12:03Z"),
state: "WA", price: 43, quantity: 134 }
] )

此示例在 $setWindowFields 阶段使用 $documentNumber 来输出每个 state 的蛋糕销售单据编号:

db.cakeSales.aggregate( [
{
$setWindowFields: {
partitionBy: "$state",
sortBy: { quantity: -1 },
output: {
documentNumberForState: {
$documentNumber: {}
}
}
}
}
] )

在示例中:

  • partitionBy: "$state"state 对集合中的文档分区CAWA 都有分区。

  • sortBy: { quantity: -1 }quantity 以降序 (-1) 对每个分区中的文档进行排序,因此最高的 quantity 位于最前面。

  • output 在名为 documentNumberForState 的新字段中设置文档编号,如以下结果所示。documentNumberForState 在每个 state 分区内都是唯一的。

{ "_id" : 4, "type" : "strawberry", "orderDate" : ISODate("2019-05-18T16:09:01Z"),
"state" : "CA", "price" : 41, "quantity" : 162, "documentNumberForState" : 1 }
{ "_id" : 2, "type" : "vanilla", "orderDate" : ISODate("2021-01-11T06:31:15Z"),
"state" : "CA", "price" : 12, "quantity" : 145, "documentNumberForState" : 2 }
{ "_id" : 0, "type" : "chocolate", "orderDate" : ISODate("2020-05-18T14:10:30Z"),
"state" : "CA", "price" : 13, "quantity" : 120, "documentNumberForState" : 3 }
{ "_id" : 1, "type" : "chocolate", "orderDate" : ISODate("2021-03-20T11:30:05Z"),
"state" : "WA", "price" : 14, "quantity" : 140, "documentNumberForState" : 1 }
{ "_id" : 5, "type" : "strawberry", "orderDate" : ISODate("2019-01-08T06:12:03Z"),
"state" : "WA", "price" : 43, "quantity" : 134, "documentNumberForState" : 2 }
{ "_id" : 3, "type" : "vanilla", "orderDate" : ISODate("2020-02-08T13:13:23Z"),
"state" : "WA", "price" : 13, "quantity" : 104, "documentNumberForState" : 3 }

创建 cakeSalesWithDuplicates 集合,其中:

  • 蛋糕销售位于加利福尼亚州 (CA) 和华盛顿州 (WA)。

  • 文档 6 至 8 与文档 5 具有相同的 quantitystate

  • 文档 9 具有与文档 4 相同的 quantitystate

  • 文档 10 包含 null quantity

  • 文档 11 缺少 quantity

db.cakeSalesWithDuplicates.insertMany( [
{ _id: 0, type: "chocolate", orderDate: new Date("2020-05-18T14:10:30Z"),
state: "CA", price: 13, quantity: 120 },
{ _id: 1, type: "chocolate", orderDate: new Date("2021-03-20T11:30:05Z"),
state: "WA", price: 14, quantity: 140 },
{ _id: 2, type: "vanilla", orderDate: new Date("2021-01-11T06:31:15Z"),
state: "CA", price: 12, quantity: 145 },
{ _id: 3, type: "vanilla", orderDate: new Date("2020-02-08T13:13:23Z"),
state: "WA", price: 13, quantity: 104 },
{ _id: 4, type: "strawberry", orderDate: new Date("2019-05-18T16:09:01Z"),
state: "CA", price: 41, quantity: 162 },
{ _id: 5, type: "strawberry", orderDate: new Date("2019-01-08T06:12:03Z"),
state: "WA", price: 43, quantity: 134 },
{ _id: 6, type: "strawberry", orderDate: new Date("2020-01-08T06:12:03Z"),
state: "WA", price: 41, quantity: 134 },
{ _id: 7, type: "strawberry", orderDate: new Date("2020-01-01T06:12:03Z"),
state: "WA", price: 34, quantity: 134 },
{ _id: 8, type: "strawberry", orderDate: new Date("2020-01-02T06:12:03Z"),
state: "WA", price: 40, quantity: 134 },
{ _id: 9, type: "strawberry", orderDate: new Date("2020-05-11T16:09:01Z"),
state: "CA", price: 39, quantity: 162 },
{ _id: 10, type: "strawberry", orderDate: new Date("2020-05-11T16:09:01Z"),
state: "CA", price: 39, quantity: null },
{ _id: 11, type: "strawberry", orderDate: new Date("2020-05-11T16:09:01Z"),
state: "CA", price: 39 }
] )

此示例在 $setWindowFields 阶段使用 $documentNumber 来输出每个 statecakeSalesWithDuplicates 文档编号:

db.cakeSalesWithDuplicates.aggregate( [
{
$setWindowFields: {
partitionBy: "$state",
sortBy: { quantity: -1 },
output: {
documentNumberForState: {
$documentNumber: {}
}
}
}
}
] )

在示例中:

  • partitionBy: "$state"state 对集合中的文档分区CAWA 都有分区。

  • sortBy: { quantity: -1 }quantity 以降序 (-1) 对每个分区中的文档进行排序,因此最高的 quantity 位于最前面。

  • output 在名为 documentNumberForState 的新字段中设置文档编号,如以下结果所示。documentNumberForState 在每个 state 分区中都是唯一的,并且具有 null quantity 和缺少 quantity 值的文档有 documentNumberForState 值。

{ "_id" : 4, "type" : "strawberry", "orderDate" : ISODate("2019-05-18T16:09:01Z"),
"state" : "CA", "price" : 41, "quantity" : 162, "documentNumberForState" : 1 }
{ "_id" : 9, "type" : "strawberry", "orderDate" : ISODate("2020-05-11T16:09:01Z"),
"state" : "CA", "price" : 39, "quantity" : 162, "documentNumberForState" : 2 }
{ "_id" : 2, "type" : "vanilla", "orderDate" : ISODate("2021-01-11T06:31:15Z"),
"state" : "CA", "price" : 12, "quantity" : 145, "documentNumberForState" : 3 }
{ "_id" : 0, "type" : "chocolate", "orderDate" : ISODate("2020-05-18T14:10:30Z"),
"state" : "CA", "price" : 13, "quantity" : 120, "documentNumberForState" : 4 }
{ "_id" : 10, "type" : "strawberry", "orderDate" : ISODate("2020-05-11T16:09:01Z"),
"state" : "CA", "price" : 39, "quantity" : null, "documentNumberForState" : 5 }
{ "_id" : 11, "type" : "strawberry", "orderDate" : ISODate("2020-05-11T16:09:01Z"),
"state" : "CA", "price" : 39, "documentNumberForState" : 6 }
{ "_id" : 1, "type" : "chocolate", "orderDate" : ISODate("2021-03-20T11:30:05Z"),
"state" : "WA", "price" : 14, "quantity" : 140, "documentNumberForState" : 1 }
{ "_id" : 5, "type" : "strawberry", "orderDate" : ISODate("2019-01-08T06:12:03Z"),
"state" : "WA", "price" : 43, "quantity" : 134, "documentNumberForState" : 2 }
{ "_id" : 6, "type" : "strawberry", "orderDate" : ISODate("2020-01-08T06:12:03Z"),
"state" : "WA", "price" : 41, "quantity" : 134, "documentNumberForState" : 3 }
{ "_id" : 7, "type" : "strawberry", "orderDate" : ISODate("2020-01-01T06:12:03Z"),
"state" : "WA", "price" : 34, "quantity" : 134, "documentNumberForState" : 4 }
{ "_id" : 8, "type" : "strawberry", "orderDate" : ISODate("2020-01-02T06:12:03Z"),
"state" : "WA", "price" : 40, "quantity" : 134, "documentNumberForState" : 5 }
{ "_id" : 3, "type" : "vanilla", "orderDate" : ISODate("2020-02-08T13:13:23Z"),
"state" : "WA", "price" : 13, "quantity" : 104, "documentNumberForState" : 6 }

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