Databases and Collections

Overview

In this guide, you can learn how to interact with MongoDB databases and collections by using the Go driver.

MongoDB organizes data into a hierarchy of the following levels:

Databases: Top-level data structures in a MongoDB deployment that store collections.
Collections: Groups of MongoDB documents. They are analogous to tables in relational databases.
Documents: Units that store literal data such as strings, numbers, dates, and other embedded documents. For more information about document field types and structure, see the Documents entry in the MongoDB Server manual.

Access a Database

You can access a database by using the Database() method on a Client instance.

The following example accesses a database named test_database:

database := client.Database("test_database")

Access a Collection

You can access a collection by using the Collection() method on a Database instance.

The following example accesses a collection named test_collection:

collection := database.Collection("test_collection")

Tip

If the provided collection name does not already exist in the database, MongoDB implicitly creates the collection when you first insert data into it.

Create a Collection

To explicity create a collection, you can use the CreateCollection() method on a Database instance.

The following example creates a collection named example_collection:

err = database.CreateCollection(context.TODO(), "example_collection")
if err != nil {
	log.Fatalf("Failed to create collection: %v", err)
}

You can specify collection options, such as maximum size and document validation rules, by passing an options.CreateCollectionOptions struct to the CreateCollection() method of a Database instance. For a full list of optional parameters, see the create command entry in the MongoDB Server manual.

Get a List of Collections

You can query for a list of collections in a database by using the ListCollections() method on a Database instance.

The following example gets a list of all the collections in a database, and then prints the collection names to the console:

cursor, err := database.ListCollections(context.TODO(), bson.D{})
if err != nil {
	log.Fatalf("Failed to list collections: %v", err)
}
defer cursor.Close(context.TODO())
for cursor.Next(context.TODO()) {
	var collectionInfo bson.M
	if err := cursor.Decode(&collectionInfo); err != nil {
		log.Fatalf("Failed to decode collection info: %v", err)
	}
	if name, ok := collectionInfo["name"].(string); ok {
		fmt.Println(name)
	} else {
		log.Println("Collection name not found or not a string")
	}
}
if err := cursor.Err(); err != nil {
	log.Fatalf("Cursor error: %v", err)
}

Delete a Collection

You can delete a collection by using the Drop() method on a Database instance.

The following example deletes a collection named test_collection:

err = database.Collection("test_collection").Drop(context.TODO())
if err != nil {
	log.Fatalf("Failed to drop collection: %v", err)
}

Warning

Dropping a Collection Deletes All Data in the Collection

Dropping a collection from your database permanently deletes all documents and all indexes within that collection.

Drop a collection only if you no longer need the data in that collection.

API Documentation

To learn more about any of the types or methods discussed in this guide, see the following API documentation:

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CRUD Operations