MongoDB datasource - Forest Documentation

The MongoDB datasource connects directly to MongoDB without requiring Mongoose or another ORM. It automatically introspects your collections by sampling documents to infer the schema.

MongoDB datasource is only available for Node.js. For Ruby, check the Mongoid datasource.

Basic usage

import { createAgent } from '@forestadmin/agent';
import { createMongoDataSource } from '@forestadmin/datasource-mongo';

const agent = createAgent(options);

agent.addDataSource(
  createMongoDataSource({
    uri: 'mongodb://localhost:27017',
    dataSource: { flattenMode: 'auto' }
  })
);

Schema introspection

Since MongoDB lacks a predefined schema, the back-end samples documents from each collection during startup to infer the structure. You can control this behavior:

createMongoDataSource({
  uri: 'mongodb://localhost:27017',
  introspection: {
    collectionSampleSize: 100,    // Documents sampled per collection
    referenceSampleSize: 10,       // References analyzed for relationships
    maxPropertiesPerObject: 30     // Maximum properties extracted as columns
  }
})

Setting sample sizes too high may slow back-end startup times.

Filtering collections

Exclude specific collections from Forest:

const agent = createAgent(options);

agent.addDataSource(
  createMongoDataSource({ uri: connectionString }),
  { exclude: ['accounts', 'accounts_bills', 'accounts_bills_items'] }
);

Flattening nested data

MongoDB stores nested BSON documents. Configure flattening to convert nested structures into columns or separate collections:

createMongoDataSource({
  uri: 'mongodb://localhost:27017',
  dataSource: {
    flattenMode: 'manual',
    flattenOptions: {
      persons: {
        asModels: ['bills'],                    // Convert to separate collections
        asFields: ['address']                   // Move to root level
        // or: asFields: ['address.city', 'address.country']
        // or: asFields: [{ field: 'address', level: 1 }]
      }
    }
  }
})

When customizing your back-end, navigate paths using these separators:

Nested fields: Use @@@ to access nested properties
Related data: Use : to navigate relationships

Example: address:city@@@name accesses the name field within city within the address relation.

Source code

This connector is open source. Browse the code or contribute on GitHub: @forestadmin/datasource-mongo.

​Basic usage

​Schema introspection

​Filtering collections

​Flattening nested data

​Data navigation

​Source code

Basic usage

Schema introspection

Filtering collections

Flattening nested data

Data navigation

Source code