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$mod (evaluation query)

APPLIES TO: MongoDB vCore

The $mod operator performs a modulo operation on the value of a field and selects documents with a specified result. This operator is useful for finding documents where a numeric field value, when divided by a divisor, leaves a specific remainder. It commonly serves for pagination, sampling data, or finding patterns in numeric sequences.

Syntax

The syntax for the $mod operator is as follows:

{
  <field>: { $mod: [ <divisor>, <remainder> ] }
}

Parameters

Description
<field> The field to perform the modulo operation on. The field must contain numeric values.
<divisor> The number to divide the field value by. Must be a positive number.
<remainder> The expected remainder after the modulo operation. Must be a non-negative number less than the divisor.

Example

Example 1: Find stores with sales divisible by 1000

The example retrieves stores where total sales are divisible by 1000 (useful for identifying round sales figures).

db.stores.find({
  "sales.totalSales": { $mod: [1000, 0] }
}).limit(2)

This query identifies stores with sales figures that are exact multiples of 1000, which might indicate promotional pricing or bulk sales patterns.

  {
    "_id": "new-store-001",
    "name": "TechWorld Electronics - Downtown Branch",
    "sales": {
      "totalSales": 5000
    },
    "createdDate": "2025-06-11T11:11:32.262Z",
    "status": "new",
    "staff": {
      "totalStaff": {
        "fullTime": 0,
        "partTime": 0
      }
    },
    "version": 1
  },
  {
    "_id": "gaming-store-mall-001",
    "name": "Gaming Paradise - Mall Location",
    "location": {
      "lat": 35.6762,
      "lon": 139.6503
    },
    "createdDate": "2025-06-11T11:13:27.180Z",
    "status": "active",
    "staff": {
      "totalStaff": {
        "fullTime": 8,
        "partTime": 12
      },
      "manager": "Alex Johnson",
      "departments": [
        "gaming",
        "accessories",
        "repairs"
      ]
    },
    "sales": {
      "totalSales": 0,
      "salesByCategory": []
    },
    "operatingHours": {
      "weekdays": "10:00-22:00",
      "weekends": "09:00-23:00"
    },
    "metadata": {
      "version": 1,
      "source": "store-management-system"
    }
  }

Example 2: Pagination-style querying

Find stores where part-time employee count leaves remainder 0 when divided by 4 (useful for creating data subsets).

db.stores.find({
  "staff.totalStaff.partTime": { $mod: [4, 0] }
})

This type of query is useful for creating consistent data partitions or implementing custom pagination logic based on field values.

  {
    "_id": "new-store-001",
    "name": "TechWorld Electronics - Downtown Branch",
    "sales": {
      "totalSales": 5000
    },
    "createdDate": "2025-06-11T11:11:32.262Z",
    "status": "new",
    "staff": {
      "totalStaff": {
        "fullTime": 0,
        "partTime": 0
      }
    },
    "version": 1
  },
  {
    "_id": "gaming-store-mall-001",
    "name": "Gaming Paradise - Mall Location",
    "location": {
      "lat": 35.6762,
      "lon": 139.6503
    },
    "createdDate": "2025-06-11T11:13:27.180Z",
    "status": "active",
    "staff": {
      "totalStaff": {
        "fullTime": 8,
        "partTime": 12
      },
      "manager": "Alex Johnson",
      "departments": [
        "gaming",
        "accessories",
        "repairs"
      ]
    },
    "sales": {
      "totalSales": 0,
      "salesByCategory": []
    },
    "operatingHours": {
      "weekdays": "10:00-22:00",
      "weekends": "09:00-23:00"
    },
    "metadata": {
      "version": 1,
      "source": "store-management-system"
    }
  }

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