$[]

項目一覧

定義
動作
例

定義

$[]

The all positional operator $[] indicates that the update operator should modify all elements in the specified array field.

$[]演算子は次のような形をとります。

{ <update operator>: { "<array>.$[]" : value } }

Use in update operations, e.g. db.collection.updateOne() and db.collection.findAndModify(), to modify all array elements for the document or documents that match the query condition. For example:

db.collection.updateOne(
   { <query conditions> },
   { <update operator>: { "<array>.$[]" : value } }
)

For an example, see Update All Elements in an Array.

動作

MongoDB 5.0 以降、更新演算子では名前が文字列ベースのドキュメントフィールドを辞書順に処理します。数値名のフィールドは、数値順に処理されます。詳細については、「更新演算子の動作」を参照してください。

`upsert`

If an upsert operation results in an insert, the query must include an exact equality match on the array field in order to use the $[] positional operator in the update statement.

For example, the following upsert operation, which uses $[] in the update document, specifies an exact equality match condition on the array field:

db.collection.updateOne(
   { myArray: [ 5, 8 ] },
   { $set: { "myArray.$[]": 10 } },
   { upsert: true }
)

If no such document exists, the operation would result in an insertion of the following document:

{ "_id" : ObjectId(...), "myArray" : [ 10, 10 ] }

If the upsert operation did not include an exact equality match and no matching documents were found to update, the upsert operation would error.

For example, the following operations would error if no matching documents were found to update:

db.emptyCollection.updateOne(
   { },
   { $set: { "myArray.$[]": 10 } },
   { upsert: true }
)
db.emptyCollection.updateOne(
   { myArray: 5 },
   { $set: { "myArray.$[]": 10 } },
   { upsert: true }
)

ネストされた配列

The $[] operator can be used for queries that traverse more than one array and nested arrays.

例は、「 $[<identifier>] を使用した入れ子配列の更新」を参照してください。

例

Update All Elements in an Array

students コレクションを次のように作成します。

db.students.insertMany( [
   { "_id" : 1, "grades" : [ 85, 82, 80 ] },
   { "_id" : 2, "grades" : [ 88, 90, 92 ] },
   { "_id" : 3, "grades" : [ 85, 100, 90 ] }
] )

To increment all elements in the grades array by 10 for all documents in the collection, use the all positional $[] operator:

db.students.updateMany(
   { },
   { $inc: { "grades.$[]": 10 } },
)

The all positional $[] operator acts as a placeholder for all elements in the array field.

操作後、students コレクションには次のドキュメントが含まれます。

{ "_id" : 1, "grades" : [ 95, 92, 90 ] }
{ "_id" : 2, "grades" : [ 98, 100, 102 ] }
{ "_id" : 3, "grades" : [ 95, 110, 100 ] }

Update All Documents in an Array

The $[] positional operator facilitates updates to arrays that contain embedded documents. To access the fields in the embedded documents, use the ドット表記 with the $[] operator.

db.collection.updateOne(
   { <query selector> },
   { <update operator>: { "array.$[].field" : value } }
)

students2 コレクションを次のように作成します。

db.students2.insertMany( [
   {
      "_id" : 1,
      "grades" : [
         { "grade" : 80, "mean" : 75, "std" : 8 },
         { "grade" : 85, "mean" : 90, "std" : 6 },
         { "grade" : 85, "mean" : 85, "std" : 8 }
      ]
   },
   {
      "_id" : 2,
      "grades" : [
         { "grade" : 90, "mean" : 75, "std" : 8 },
         { "grade" : 87, "mean" : 90, "std" : 5 },
         { "grade" : 85, "mean" : 85, "std" : 6 }
      ]
   }
] )

To modify the value of the std field for all elements in the grades array, use the positional $[] operator:

db.students2.updateMany(
   { },
   { $inc: { "grades.$[].std" : -2 } },
)

操作後、コレクションには次のドキュメントが含まれます。

{
   "_id" : 1,
   "grades" : [
      { "grade" : 80, "mean" : 75, "std" : 6 },
      { "grade" : 85, "mean" : 90, "std" : 4 },
      { "grade" : 85, "mean" : 85, "std" : 6 }
   ]
}
{
   "_id" : 2,
   "grades" : [
      { "grade" : 90, "mean" : 75, "std" : 6 },
      { "grade" : 87, "mean" : 90, "std" : 3 },
      { "grade" : 85, "mean" : 85, "std" : 4 }
   ]
}

Update Arrays Specified Using a Negation Query Operator

results コレクションを次のように作成します。

db.results.insertMany( [
   { "_id" : 1, "grades" : [ 85, 82, 80 ] },
   { "_id" : 2, "grades" : [ 88, 90, 92 ] },
   { "_id" : 3, "grades" : [ 85, 100, 90 ] }
] )

To increment all elements in the grades array by 10 for all documents except those with the value 100 in the grades array, use the all positional $[] operator:

db.results.updateMany(
   { "grades" : { $ne: 100 } },
   { $inc: { "grades.$[]": 10 } },
)

The all positional $[] operator acts as a placeholder for all elements in the array field.

操作後、students コレクションには次のドキュメントが含まれます。

{ "_id" : 1, "grades" : [ 95, 92, 90 ] }
{ "_id" : 2, "grades" : [ 98, 100, 102 ] }
{ "_id" : 3, "grades" : [ 85, 100, 90 ] }

`$[<identifier>]`を使用した入れ子配列のアップデート

The $[] positional operator, in conjunction with filter $[<identifier>] positional operator can be used to update nested arrays.

次のドキュメントを使用してコレクション students3 を作成します。

db.students3.insertMany( [
   { "_id" : 1,
      "grades" : [
        { type: "quiz", questions: [ 10, 8, 5 ] },
        { type: "quiz", questions: [ 8, 9, 6 ] },
        { type: "hw", questions: [ 5, 4, 3 ] },
        { type: "exam", questions: [ 25, 10, 23, 0 ] },
      ]
   }
] )

typeに関係なく、ネストされたgrades.questions配列内で8以上のすべての値をアップデートするには、

db.students3.updateMany(
   {},
   { $inc: { "grades.$[].questions.$[score]": 2 } },
   { arrayFilters: [  { "score": { $gte: 8 } } ] }
)

The updated documents look like this:

{
  _id: 1,
  grades: [
    { type: 'quiz', questions: [ 12, 10, 5 ] },
    { type: 'quiz', questions: [ 10, 11, 6 ] },
    { type: 'hw', questions: [ 5, 4, 3 ] },
    { type: 'exam', questions: [ 27, 12, 25, 0 ] }
  ]
}

Tip

以下も参照してください。

戻る

$ (update)

$[<identifier>]

$[]

定義

動作

upsert