Mongoengine is a Python Object-Document Mapper (ODM) that allows easy integration of MongoDB with Python applications. With the help of mongoengine, you can define your data models as Python classes and interact with MongoDB in a more intuitive and Pythonic way.

In mongoengine, you can define metadata for your models using the meta attribute. This metadata provides additional settings and options for your models. Let’s take a look at some common use cases for configuring metadata in mongoengine.

Collection Name

By default, mongoengine uses the class name converted to snake case as the collection name in MongoDB. However, you can customize the collection name by setting the collection attribute in the meta class.

class MyModel(mongoengine.Document):
    meta = {'collection': 'my_custom_collection'}
    # rest of the model definition

In the above example, the MyModel documents will be stored in the collection named “my_custom_collection” instead of the default “my_model”.

Indexes

Indexes are crucial for improving query performance in MongoDB. You can define indexes for your models using the indexes attribute in the meta class. The value of the indexes attribute should be a list of dictionaries, where each dictionary represents an index specification.

class MyModel(mongoengine.Document):
    meta = {
        'indexes': [
            {'fields': [('field1', 'asc'), ('field2', 'desc')]},
            {'fields': ['field3'], 'unique': True}
        ]
    }
    # rest of the model definition

In the above example, we define two indexes for the MyModel. The first index is a compound index on “field1” ascending and “field2” descending. The second index is a single field index on “field3” with a unique constraint.

Ordering

You can specify the default ordering of query results using the ordering attribute in the meta class. The value of the ordering attribute should be a list of fields to order by.

class MyModel(mongoengine.Document):
    meta = {'ordering': ['-created_at']}
    # rest of the model definition

In the above example, the query results of MyModel.objects.all() will be ordered by the “created_at” field in descending order by default.

Additional Configuration

Other than the above examples, mongoengine provides various other options that can be configured using the meta attribute. Some common options include allow_inheritance, db_alias, abstract, strict, etc. You can refer to the mongoengine documentation for a full list of available options.

Overall, using the meta attribute in mongoengine allows you to customize the behavior and settings of your models, providing flexibility and control over the MongoDB integration in your Python application.