`$createUUID`

項目一覧

定義
構文
動作
例

定義

The $createUUID expression takes no arguments and returns a UUID BSON type (i.e. a BinData with subtype=4). The UUID is a version 4 UUID conforming to RFC 4122.

$createUUID: A $createUUID expression takes the form of an empty object {}.

構文

The $createUUID expression is an empty object {} and has no internal syntax.

動作

Pass $createUUID: {} in your aggregation pipeline to generate a UUID value.

例

The following examples demonstrate a basic use of the $createUUID expression.

{$project: {
  a: {$createUUID: {}}
  b: {$createUUID: {}}
}}

{
 a: UUID('e14ac078-b627-48e8-b009-77dbd7150e75')
 b: UUID(‘f18689fe-6dfc-4823-a01e-32792f0091fe’)
}

You can use a $toString expression to convert the output of your $createUUID expression to a string value.

{$project: {
  a: {$toString: {$createUUID: {}}}
}}

{
 a: 'e14ac078-b627-48e8-b009-77dbd7150e75'
}

{$project: {
  a: {$createUUID: {“foo”: “bar”}}
}}

Error– $createUUID does not accept arguments.

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