$mod (aggregation)

Definition定义

$mod

Divides one number by another and returns the remainder.将一个数字除以另一个数字，然后返回余数。

The $mod expression has the following syntax:$mod表达式语法如下：

{ $mod: [ <expression1>, <expression2> ] }

The first argument is the dividend, and the second argument is the divisor; i.e. first argument is divided by the second argument.第一个参数是被除数，第二个参数是除数；第一个参数被第二个参数分割。

The arguments can be any valid expression as long as they resolve to numbers. 参数可以是任何有效的表达式，只要它们解析为数字。For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。

Example示例

Consider a planning collection with the following documents:考虑使用以下文档的planning集合：

{ "_id" : 1, "project" : "A", "hours" : 80, "tasks" : 7 }
{ "_id" : 2, "project" : "B", "hours" : 40, "tasks" : 4 }

The following aggregation uses the $mod expression to return the remainder of the hours field divided by the tasks field:以下聚合使用$mod表达式返回hours字段除以tasks字段的余数：

db.planning.aggregate(
   [
     { $project: { remainder: { $mod: [ "$hours", "$tasks" ] } } }
   ]
)

The operation returns the following results:该操作返回以下结果：

{ "_id" : 1, "remainder" : 3 }
{ "_id" : 2, "remainder" : 0 }