MongoDB Data Validation Rules

What Are MongoDB Data Validation Rules?

Data validation rules in MongoDB define criteria that documents must meet before being inserted or updated in a collection.

These rules help prevent invalid or inconsistent data from entering your database.

• Enforce field types and required fields.
• Set value ranges or string patterns.
• Control document structure and nested fields.

Defining Validation Rules Using JSON Schema

MongoDB supports JSON Schema, a powerful and expressive way to define validation rules.

You can specify required fields, data types, value constraints, and more.

• Use the $jsonSchema operator in the validator option.
• Define required fields with the 'required' keyword.
• Specify field types with the 'bsonType' keyword.
• Add constraints like 'minimum', 'maximum', 'pattern', and 'enum'.

Example: Creating a Collection with Validation

You can create a collection with validation rules using the 'validator' option in the createCollection command.

Validation Levels and Actions

MongoDB allows you to control how strictly validation rules are enforced using validationLevel and validationAction options.

• validationLevel: 'off', 'moderate', or 'strict' determines when validation occurs.
• validationAction: 'warn' or 'error' controls whether invalid documents cause errors or warnings.

Using Expression-Based Validators

Besides JSON Schema, MongoDB supports expression-based validators using query operators to define custom validation logic.

• Use MongoDB query operators like $and, $or, $exists, $type in the validator.
• Allows flexible validation beyond JSON Schema capabilities.