MongoDB - 嵌入式文档列表中的$ addToSet

$addToSet使用通常的mongodb相等规则:它将进行深入的值值比较,因此以下两个文档是相同的:

{ name: "John", hobbies: ["coding", "drinking", "chess"] }
{ hobbies: ["coding", "drinking", "chess"], name: "John" }

(文件内的订单不保证,所以它们是相同的)

而那些不是(成对):

// compare to:
{ name: "John", hobbies: ["chess", "coding", "drinking"] } 

// in arrays, the order matters:
{ name: "John", hobbies: ["coding", "drinking", "chess"] } 

// field names and values are case sensitive
{ Name: "John", hobbies: ["chess", "coding", "drinking"] } 
{ name: "john", hobbies: ["chess", "coding", "drinking"] } 

// additional field:
{ name: "John", lastName: "Doe", hobbies: ["chess", "coding", "drinking"] }

// missing field:
{ name: "John" }

请注意,这里没有特殊字段.您可以添加一个_id字段,但它没有特殊的语义,并且将被视为与任何其他字段一样.