MongoDB Mongoose

Overview

This node allows users to interact with MongoDB databases using the Mongoose Object Data Modeling (ODM) library. It supports a variety of operations such as finding one document, finding multiple documents, creating, updating, deleting, counting, and running aggregation pipelines on collections within a MongoDB database.

The "Find One" operation specifically retrieves a single document from a specified collection that matches a given query filter. This is useful when you want to fetch a unique or first matching record based on certain criteria.

Common scenarios:

• Retrieving user details by a unique identifier or email.
• Fetching configuration or settings documents where only one record is expected.
• Querying for a specific order or transaction in an e-commerce system.

Practical example:
You want to find a user document in the "users" collection where the username is "johndoe". You provide a query { "username": "johndoe" } and optionally specify which fields to return, such as name and email.

Properties

Output

The output is an array of items, each containing a json property with the following structure for the "Find One" operation:

• The main content is the found document represented as a JSON object with the requested fields.
• If no document matches the query, the output will contain null as the result.
• If "Include Query Info" is enabled, the output JSON also contains metadata about the executed query, including:
  • The operation type (findOne)
  • The original query object used
  • The options applied during the query (such as selected fields)

Example output JSON (simplified):

{
  "result": {
    "_id": "60d5ec49f8d2c4567a123456",
    "name": "John Doe",
    "email": "john@example.com"
  },
  "query": {
    "name": "John Doe"
  },
  "options": {
    "selectFields": {
      "_id": 1,
      "name": 1,
      "email": 1
    }
  },
  "operation": "findOne"
}

If no document is found, "result" will be null.

Dependencies

• Requires a MongoDB instance accessible via a connection string.
• Uses Mongoose ODM library to interact with MongoDB.
• Requires an API key credential configured in n8n for MongoDB access.
• Supports multi-database connections by specifying the database name or using the default from credentials.
• The node expects a valid Mongoose schema definition for the target collection to properly parse and cast query parameters.

Troubleshooting

• Connection errors:
  Errors like "MongoDB connection error", "host not found", or "connection refused" indicate issues with the connection string, network, or MongoDB server availability. Verify the connection string, hostname/IP, port, and ensure MongoDB is running.

• Authentication failures:
  Messages mentioning authentication failure suggest incorrect username, password, or authentication database settings. Double-check credentials and permissions.

• Invalid JSON format:
  Input properties such as Query, Schema Definition, or Select Fields must be valid JSON strings. Invalid JSON will cause parsing errors. Use proper JSON syntax.

• Limit exceeded:
  The node enforces a maximum limit of 10,000 documents for safety. Setting a higher limit will throw an error.

• Large result sets warning:
  When retrieving many documents (not typical for "findOne"), a warning is logged suggesting adding indexes or refining filters.

• Schema mismatch:
  Incorrect or incomplete schema definitions may cause unexpected behavior or casting errors. Ensure the schema matches the actual collection structure.

• Timeouts:
  Queries taking longer than the specified timeout (default 30 seconds) will fail. Adjust the "Query Timeout" option if necessary.

Links and References

• Mongoose Documentation — Official guide for defining schemas and models.
• MongoDB Query Operators — Reference for building query objects.
• MongoDB Aggregation Pipeline — For advanced data processing (not directly relevant to "findOne" but supported by the node).
• n8n Documentation — General documentation for using nodes and credentials in n8n.