$setEquals (aggregation)

項目一覧

定義
動作
例

定義

$setEquals

Compares two or more arrays and returns true if they have the same distinct elements and false otherwise.

$setEqualsの構文は次のとおりです。

{ $setEquals: [ <expression1>, <expression2>, ... ] }

The arguments can be any valid 式 as long as they each resolve to an array. For more information on expressions, see 式演算子.

動作

$setEquals performs set operation on arrays, treating arrays as sets. If an array contains duplicate entries, $setEquals ignores the duplicate entries. $setEquals ignores the order of the elements.

セットにネストされた配列要素が含まれている場合、 $setEqualsはネストされた配列に下降せず、最上位の配列を評価します。

例	結果
`{ $setEquals: [ [ "a", "b", "a" ], [ "b", "a" ] ] }`	`true`
`{ $setEquals: [ [ "a", "b" ], [ [ "a", "b" ] ] ] }`	`false`

例

以下のドキュメントを持つbakeryOrdersコレクションを考えてみましょう。

db.bakeryOrders.insertMany( [
   { _id: 0, cakes: ["chocolate", "vanilla"], cupcakes: ["chocolate", "vanilla"] },
   { _id: 1, cakes: ["chocolate", "vanilla"], cupcakes: ["vanilla", "chocolate"] },
   { _id: 2, cakes: ["chocolate", "chocolate"], cupcakes: ["chocolate"] },
   { _id: 3, cakes: ["vanilla"], cupcakes: ["chocolate"] },
   { _id: 4, cakes: ["vanilla"], cupcakes: [] }
] )

The following operation uses the $setEquals operator to determine if the cakes array and the cupcakes array in each order contain the same flavors:

db.bakeryOrders.aggregate(
   [
      {
         $project: {
            _id: 0,
            cakes: 1,
            cupcakes: 1,
            sameFlavors: { $setEquals: [ "$cakes", "$cupcakes" ] }
         }
      }
   ] )

注意

$project

The $project stage specifies which fields are included in the output documents. In this example, the $project stage:

Excludes the _id field from the output.
Includes the cakes and cupcakes fields in the output.
Outputs the result of the $setEquals operator in a new field called sameFlavors.

この操作は次の結果を返します。

{
 cakes: [ "chocolate", "vanilla" ],
 cupcakes: [ "chocolate", "vanilla" ],
 sameFlavors: true
},
{
 cakes: [ "chocolate", "vanilla" ],
 cupcakes: [ "vanilla", "chocolate" ],
 sameFlavors: true
},
{
 cakes: [ "chocolate", "chocolate" ],
 cupcakes: [ "chocolate" ],
 sameFlavors: true
},
{
 cakes: [ "vanilla" ],
 cupcakes: [ "chocolate" ],
 sameFlavors: false
},
{
   cakes: [ "vanilla" ],
   cupcakes: [],
   sameFlavors: false
}

戻る

$setDifference

$setField