MongoEngine - Dynamic Schema

One of the advantages of MongoDB database is that it supports dynamic schema. To create a class that supports dynamic schema, subclass it from DynamicDocument base class. Following is the Student class with dynamic schema −

>>> class student(DynamicDocument):
... name=StringField()

The first step is to add first Document as before.

>>> s1=student()
>>> s1.name="Tara"
>>> connect( mydb )
>>> s1.save()

Now add another attribute to second document and save.

>>> s2=student()
>>> setattr(s2, age ,20)
>>> s2.name= Lara 
>>> s2.save()

In the database, student collection will show two documents with dynamic schema.

The meta dictionary of document class can use a Capped Collection by specifying max_documents and max_size.

max_documents − The maximum number of documents that is allowed to be stored in the collection.

max_size − The maximum size of the collection in bytes. max_size is rounded up to the next multiple of 256 by MongoDB internally and mongoengine before.

If max_size is not specified and max_documents is, max_size defaults to 10485760 bytes (10MB).

Other parameters of Document class are psted below −