$sortArray (aggregation)

Sort by Document Fields按文档字段排序

If the array elements are documents, you can sort by a document field. 如果数组元素是文档，则可以按文档字段进行排序。Specify the field name and a sort direction, ascending (1), or descending (-1 ).指定字段名称和排序方向，升序（1）或降序（-1）。

{
   input: <array-of-documents>,
   sortBy: { <document-field>: <sort-direction> }
}

Sort by Value按值排序

To sort the whole array by value, or to sort by array elements that are not documents, identify the input array and specify 1 for an ascending sort or -1 for descending sort in the sortBy parameter.要按值对整个数组进行排序，或按非文档的数组元素进行排序，请识别输入数组，并在sortBy参数中为升序指定1或为降序指定-1。

{
   input: <array-of-documents>,
   sortBy: <sort-direction>
}

Considerations注意事项

• There is no implicit array traversal on the sort key.排序键上没有隐式数组遍历。
• Positional operators are not supported. 不支持位置运算符。A field name like "values.1" denotes a sub-field called "1" in the values array. 类似“values.1”的字段名称表示values数组中名为“1”的子字段。It does not refer to the item at index 1 in the values array.它没有引用values数组中索引1处的项。
• When a whole array is sorted, the sort is lexicographic. 当对整个数组进行排序时，排序是字典式的。The aggregation $sort stage, behaves differently. 聚合$sort阶段的行为不同。See $sort for more details.有关更多详细信息，请参阅$sort。
• When an array is sorted by a field, any documents or scalars that do not have the specified field are sorted equally. 当数组按字段排序时，任何没有指定字段的文档或标量都将按相同顺序排序。The resulting sort order is undefined.生成的排序顺序未定义。
• null values and missing values sort equally.值和缺失值排序相等。

Sort Stability排序稳定性

The stability of the sort is not specified. 未指定排序的稳定性。Users should not rely on $sortArray to use a particular sorting algorithm.用户不应该依赖$sortArray来使用特定的排序算法。

Sort on a Field按字段排序

Sort on a field within an array element:对数组元素中的字段进行排序：

db.engineers.aggregate( [
   { $project:
      {
          _id: 0,
          result:
            {
               $sortArray: { input: "$team", sortBy: { name: 1 } }
            }
      }
   }
] )

The name field is a sub-element in the team array. The operation returns the following results:name字段是team数组中的一个子元素。该操作返回以下结果：

{
   result:
   [
      {
        name: 'charlie',
        age: 42,
        address: { street: '12 French St', city: 'New Brunswick' }
      },
      {
        name: 'dallas',
        age: 36,
        address: { street: '12 Cowper St', city: 'Palo Alto' }
      },
      {
        name: 'pat',
        age: 30,
        address: { street: '12 Baker St', city: 'London' }
      }
   ]
}

Sort on a Subfield按子字段排序

The address field is a document with subfields of its own. Use dot notation to sort the array based on a subfield:address字段是一个具有自己的子字段的文档。使用点表示法根据子字段对数组进行排序：

db.engineers.aggregate( [
   {
      $project:
         {
                _id: 0,
                result:
               {
                  $sortArray:
                     {
                        input: "$team",
                        sortBy: { "address.city": -1 }
                     }
               }
             }
   }
] )

The sort direction is descending because the sortBy value is "-1".排序方向是递减的，因为sortBy值是“-1”。

{
  result: [
    {
      name: 'dallas',
      age: 36,
      address: { street: '12 Cowper St', city: 'Palo Alto' }
    },
    {
      name: 'charlie',
      age: 42,
      address: { street: '12 French St', city: 'New Brunswick' }
    },
    {
      name: 'pat',
      age: 30,
      address: { street: '12 Baker St', city: 'London' }
    }
  ]
}

Sort on Multiple Fields按多个字段排序

Specify multiple index fields to do a compound sort:指定多个索引字段以执行复合排序：

db.engineers.aggregate( [
   {
      $project:
         {
            _id: 0,
            result:
               {
                  $sortArray:
                     {
                        input: "$team",
                        sortBy: { age: -1, name: 1 }
                     }
               }
         }
    }
 ] )

Example output:示例输出：

{
  name: 'charlie',
  age: 42,
  address: { street: '12 French St', city: 'New Brunswick' }
},
{
  name: 'dallas',
  age: 36,
  address: { street: '12 Cowper St', city: 'Palo Alto' }
},
{
  name: 'pat',
  age: 30,
  address: { street: '12 Baker St', city: 'London' }
}

Sort an Array of Integers对整数数组进行排序

This example specifies an input array directly. The values are all the same type, Int32:此示例直接指定一个输入数组。这些值都是相同的类型，Int32：

db.engineers.aggregate( [
   {
      $project:
         {
            _id: 0,
            result:
               {
                  $sortArray:
                     {
                         input: [ 1, 4, 1, 6, 12, 5 ],
                         sortBy: 1
                     }
               }
         }
   }
] )

Example output:输出示例：

[ { result: [ 1, 1, 4, 5, 6, 12 ] } ]

The input array has a "1" in position 0 and position 2. 输入数组在位置0和位置2有一个“1”。The ones are grouped together in the results, but their are no guarantees regarding how the group of ones is sorted relative to their original order.在结果中，它们被分组在一起，但它们并不能保证如何相对于原始顺序对一组进行排序。

Sort on Mixed Type Fields在混合类型字段上排序

This example specifies an input array directly. 此示例直接指定一个输入数组。The values have different types:这些值具有不同的类型：

db.engineers.aggregate( [
   {
      $project:
         {
            _id: 0,
            result:
            {
               $sortArray:
                  {
                     input: [ 20, 4, { a: "Free" }, 6, 21, 5, "Gratis",
                             { a: null }, { a: { sale: true, price: 19 } },
                             Decimal128( "10.23" ), { a: "On sale" } ],
                     sortBy: 1
                  }
            }
         }
   }
] )

Example output:输出示例：

{ result: [
      4,
      5,
      6,
      Decimal128("10.23"),
      20,
      21,
      'Gratis',
      { a: null },
      { a: 'Free' },
      { a: 'On sale' },
      { a: { sale: true, price: 19 } }
] }

The results are ordered.结果是有序的。

In contrast, after changing the sortBy field to sort on the one of the document fields, sortBy: { a: 1 }, the sort order for the scalar and null values is undefined:相反，在将sortBy字段更改为对其中一个文档字段sortBy: { a: 1 }进行排序后，标量值和null值的排序顺序未定义：

{ result: [
     20,
     4,
     6,
     21,
     5,
     'Gratis',
     { a: null },
     Decimal128("10.23"),
     { a: 'Free' },
     { a: 'On sale' },
     { a: { sale: true, price: 19 } }
] }