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Schema Validation

On this page

  • Overview
  • JSON Schema Validation
  • Implement Schema Validation
  • Example
  • Additional Information
  • API Documentation

In this guide, you can learn how to use the Rust driver to implement schema validation for your MongoDB collections.

To implement schema validation, you must provide a JSON schema that consists of a set of a validation rules. If you implement schema validation, the server only allows you to run write operations that follow the validation rules. Use schema validation to restrict data types and value ranges of document fields in a specified collection.

You can define schema validation rules when creating a collection by using driver methods, or you can add them to an existing collection by using the collMod MongoDB command. This guide only describes how to enable schema validation when creating a collection. To learn more about enabling schema validation on existing collections, see collMod in the Server manual.

Before creating a collection with schema validation rules, you must define a JSON schema.

The JSON schema is a JSON object that contains key-value pairs specifying the validation rules for your collection. At the top level, this object must include a $jsonSchema object. The $jsonSchema object includes the following fields:

  • title: sets an optional description for the schema.

  • required: specifies a list of required fields for each document in your collection.

  • properties: sets property requirements for individual fields.

For a full list of JSON schema object fields, see JSON Schema in the Server manual.

You can implement schema validation by passing your schema and related options in an instance of CreateCollectionOptions to the create_collection() method. You can build a CreateCollectionOptions instance by using the CreateCollectionOptions::builder() method.

Note

Instantiating Options

The Rust driver implements the Builder design pattern for the creation of many different types, including CreateCollectionOptions. You can use each type's builder() method to construct an options instance by chaining option builder functions one at a time.

Call the following CreateCollectionOptions::builder() functions to specify the validation options for the new collection:

Method
Description
validator()

Specifies validation rules for a collection by passing a JSON schema.

For more information, see the JSON Schema Validation section on this page.

validation_level()

Specifies which insert and update operations are subject to the validation rules.

Possible values: ValidationLevel::Off, ValidationLevel::Strict, ValidationLevel::Moderate.

validation_action()

Specifies whether the driver throws an error or a warning if you insert documents that don't follow the validation rules.

Possible values: ValidationAction::Error, ValidationAction::Warn.

This example creates a collection called survey_answers with the following validation specifications:

  • The validator() method receives a JSON schema specifying that the answer field in each document must have a value of "yes" or "no".

  • The validation_action() method specifies whether the driver raises an Error when a write operation violates a validation rule.

  • The validation_level() method specifies that the validation is Moderate, so the validation rules apply only to inserts and updates on existing valid documents.

let validator =
doc! {
"$jsonSchema": doc! {
"bsonType": "object",
"title": "Answer Value Validation",
"properties": doc! {
"answer": doc! {
"enum": vec! [ "yes", "no" ],
}
}
}
};
let validation_opts = CreateCollectionOptions::builder()
.validator(validator)
.validation_action(Some(ValidationAction::Error))
.validation_level(Some(ValidationLevel::Moderate))
.build();
db.create_collection("survey_answers", validation_opts).await?;

The following documents follow the validation rules and can be successfully inserted:

{
"_id": { ... },
"question": "Do you like to exercise?",
"answer": "yes"
},
{
"_id": { ... },
"question": "Do you like to play computer games?",
"answer": "no"
}

However, if you attempt to insert the following document, the server raises an error because the value of answer does not match any of the valid options:

{
"_id": { ... },
"question": "Do you like to exercise?",
"answer": "depends on my mood"
}

Tip

Bypass Schema Validation

To bypass a collection's validation rules, set the bypass_document_validation field to true in the write method's options parameter. This ignores any validation rules on the collection and any exemptions of them defined by the validation_level.

To see an example of how to specify this setting in the options for the insert_one() method, see the Modify insert_one Behavior section of the Insert Documents guide.

To learn more about the MongoDB Server operations mentioned on this page, see the following documentation in the Server manual:

To learn more about setting validation levels and actions, see the following API documentation:

To learn more about any other methods or types referenced in this guide, see the following documentation:

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