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Inheritance is off by default (MongoEngine/mongoengine#122)

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This commit is contained in:
Ross Lawley
2012-10-17 11:36:18 +00:00
parent 6f29d12386
commit 3d5b6ae332
20 changed files with 245 additions and 177 deletions
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30
docs/guide/defining-documents.rst
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@@ -462,9 +462,10 @@ If a dictionary is passed then the following options are available:
The fields to index. Specified in the same format as described above.
:attr:`cls` (Default: True)
If you have polymorphic models that inherit and have `allow_inheritance`
turned on, you can configure whether the index should have the
:attr:`_cls` field added automatically to the start of the index.
If you have polymorphic models that inherit and have
:attr:`allow_inheritance` turned on, you can configure whether the index
should have the :attr:`_cls` field added automatically to the start of the
index.
:attr:`sparse` (Default: False)
Whether the index should be sparse.
@@ -573,7 +574,9 @@ defined, you may subclass it and add any extra fields or methods you may need.
As this is new class is not a direct subclass of
:class:`~mongoengine.Document`, it will not be stored in its own collection; it
will use the same collection as its superclass uses. This allows for more
convenient and efficient retrieval of related documents::
convenient and efficient retrieval of related documents - all you need do is
set :attr:`allow_inheritance` to True in the :attr:`meta` data for a
document.::
# Stored in a collection named 'page'
class Page(Document):
@@ -585,25 +588,20 @@ convenient and efficient retrieval of related documents::
class DatedPage(Page):
date = DateTimeField()
.. note:: From 0.7 onwards you must declare `allow_inheritance` in the document meta.
.. note:: From 0.8 onwards you must declare :attr:`allow_inheritance` defaults
to False, meaning you must set it to True to use inheritance.
Working with existing data
--------------------------
To enable correct retrieval of documents involved in this kind of heirarchy,
an extra attribute is stored on each document in the database: :attr:`_cls`.
These are hidden from the user through the MongoEngine interface, but may not
be present if you are trying to use MongoEngine with an existing database.
For this reason, you may disable this inheritance mechansim, removing the
dependency of :attr:`_cls`, enabling you to work with existing databases.
To disable inheritance on a document class, set :attr:`allow_inheritance` to
``False`` in the :attr:`meta` dictionary::
As MongoEngine no longer defaults to needing :attr:`_cls` you can quickly and
easily get working with existing data. Just define the document to match
the expected schema in your database. If you have wildly varying schemas then
a :class:`~mongoengine.DynamicDocument` might be more appropriate.
# Will work with data in an existing collection named 'cmsPage'
class Page(Document):
title = StringField(max_length=200, required=True)
meta = {
'collection': 'cmsPage',
'allow_inheritance': False,
'collection': 'cmsPage'
}