Validations In MongoDB

MongoDB provides document validation capabilities to enforce rules on the structure and content of documents stored in collections.

Document validation ensures that data inserted or updated in a collection adheres to predefined rules, such as field types, value ranges, presence of certain fields, and more.

This helps maintain data integrity and consistency within the database.

Document Validation Rules:

Document validation rules are specified using JSON Schema validation expressions.

MongoDB supports a subset of JSON Schema validation features for document validation.

Document Validation In Collection:

{
  $jsonSchema: {
    bsonType: "object",
    required: ["firstName", "lastName", "age", "profession"],
    properties: {
      firstName: {
        bsonType: "string",
        description: "must be a string and is required"
      },
      lastName: {
        bsonType: "string",
        description: "must be a string and is required"
      },
      age: {
        bsonType: "int",
        minimum: 0,
        maximum: 120,
        description: "must be an integer in the range [0, 120]"
      },
     profession: {
        bsonType: "string",
        description: "must be a string and is required"
      },
    }
  }
}

bsonType: Specifies the type of the field.
required: Specifies the required fields.
properties: Defines the properties of the document and their validation criteria.

Enabling Document Validation in Collection:

To enable document validation on a collection, we can specify validation rules when creating the collection or add validation rules to an existing collection using the "collMod" command.

Create Collection with Validation:

Example:

db.createCollection("your_collection_name", {
  validator: {
    {
      $jsonSchema: {
        bsonType: "object",
        required: ["firstName", "lastName", "age", "profession"],
        properties: {
          firstName: {
          bsonType: "string",
          description: "must be a string and is required"
        },
        lastName: {
          bsonType: "string",
          description: "must be a string and is required"
        },
        age: {
          bsonType: "int",
          minimum: 0,
          maximum: 120,
          description: "must be an integer in the range [0, 120]"
        },
        profession: {
          bsonType: "string",
          description: "must be a string and is required"
        },
      }
     }
    }
  }
})

Example:

db.runCommand({
  collMod: "your_collection_name",
  validator: {
    $jsonSchema: {
       bsonType: "object",
        required: ["firstName", "lastName", "age", "profession"],
        properties: {
          firstName: {
          bsonType: "string",
          description: "must be a string and is required"
        },
        lastName: {
          bsonType: "string",
          description: "must be a string and is required"
        },
        age: {
          bsonType: "int",
          minimum: 0,
          maximum: 120,
          description: "must be an integer in the range [0, 120]"
        },
        profession: {
          bsonType: "string",
          description: "must be a string and is required"
        },
    }
  },
  validationLevel: "strict",
  validationAction: "error"
})

Note: Adding Validation Rules to an Existing Collection:

Validation Options:

MongoDB provides options to control the behavior of document validation:

validationLevel: Specifies the strictness of validation. It can be "off", "strict", or "moderate".
validationAction: Specifies the action to take when a validation rule is violated. It can be "error" or "warn".

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