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$rank (aggregation)

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版本 5.0 中的新增功能

$rank

返回一个文档在 $setWindowFields 阶段分区中相对于其他文档的位置(称为排名)。

The sortBy field value in the $setWindowFields stage determines the document rank. When used with the $rank operator, sortBy can only take one field as its value. For more information on how MongoDB compares fields with different types, see BSON comparison order.

If multiple documents occupy the same rank, $rank places the document with the subsequent value at a rank with a gap (see 行为).

$rank 只能在 $setWindowFields 阶段使用。

$rank 语法:

{ $rank: { } }

$rank不接受任何参数。

提示

另请参阅:

$rank$denseRank differ in how they rank duplicate sortBy field values. For example, with sortBy field values of 7, 9, 9, and 10:

  • $denseRank ranks the values as 1, 2, 2, and 3. The duplicate 9 values have a rank of 2, and 10 has a rank of 3. There is no gap in the ranks.

  • $rank ranks the values as 1, 2, 2, and 4. The duplicate 9 values have a rank of 2, and 10 has a rank of 4. There is a gap in the ranks for 3.

sortBy 字段值为 null 的文档或缺少 sortBy 字段的文档根据 BSON 比较顺序分配排名。

See the example in Rank Partitions Containing Duplicate Values, Nulls, or Missing Data.

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 }
] )

This example uses $rank in the $setWindowFields stage to output the quantity rank of the cake sales for each state:

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

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 sets the rankQuantityForState field to the quantity rank using $rank, as shown in the following results.

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

This example shows how to use dates with $rank in the $setWindowFields stage to output the orderDate rank of the cake sales for each state:

db.cakeSales.aggregate( [
{
$setWindowFields: {
partitionBy: "$state",
sortBy: { orderDate: 1 },
output: {
rankOrderDateForState: {
$rank: {}
}
}
}
}
] )

在示例中:

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

  • sortBy: { orderDate: 1 }orderDate 升序 (1) 对每个分区中的文档进行排序,因此最早的 orderDate 位于最前面。

  • output sets the rankOrderDateForState field to the orderDate rank using $rank, as shown in the following results.

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

This example uses $rank in the $setWindowFields stage to output the quantity rank from the cakeSalesWithDuplicates collection for each state:

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

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 sets the rankOrderDateForState field to the quantity rank using $rank

在以下示例输出中:

  • Documents with the same quantity and state have the same rank. If documents have the same rank, there is a gap between that rank and the next rank.

  • 包含 null quantity 的文档以及缺失 quantity 的文档在 CA 分区的输出中排名最低。这种排序是按照 BSON 比较顺序分配排名的结果,在本示例中,BSON 将 null 和缺失值排序在数字值之后。

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

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