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# Upgrading

## 0.5 to 0.6

Embedded Documents - if you had a pk field you will have to rename it from _id to pk as pk is no longer a property of Embedded Documents.

Reverse Delete Rules in Embedded Documents, MapFields and DictFields now throw an InvalidDocument error as they aren’t currently supported.

Document._get_subclasses - Is no longer used and the class method has been removed.

Document.objects.with_id - now raises an InvalidQueryError if used with a filter.

FutureWarning - A future warning has been added to all inherited classes that don’t define allow_inheritance in their meta.

You may need to update pyMongo to 2.0 for use with Sharding.

## 0.4 to 0.5

There have been the following backwards incompatibilities from 0.4 to 0.5. The main areas of changed are: choices in fields, map_reduce and collection names.

### Choice options:

Are now expected to be an iterable of tuples, with the first element in each tuple being the actual value to be stored. The second element is the human-readable name for the option.

### PyMongo / MongoDB

map reduce now requires pymongo 1.11+- The pymongo merge_output and reduce_output parameters, have been depreciated.

More methods now use map_reduce as db.eval is not supported for sharding as such the following have been changed:

> - `sum()`
> - `average()`
> - `item_frequencies()`

### Default collection naming

Previously it was just lowercase, its now much more pythonic and readable as its lowercase and underscores, previously

    class MyAceDocument(Document):
        pass

    MyAceDocument._meta['collection'] == myacedocument

In 0.5 this will change to

    class MyAceDocument(Document):
        pass

    MyAceDocument._get_collection_name() == my_ace_document

To upgrade use a Mixin class to set meta like so

    class BaseMixin(object):
        meta = {
            'collection': lambda c: c.__name__.lower()
        }

    class MyAceDocument(Document, BaseMixin):
        pass

    MyAceDocument._get_collection_name() == "myacedocument"

Alternatively, you can rename your collections eg

    from mongoengine.connection import _get_db
    from mongoengine.base import _document_registry

    def rename_collections():
        db = _get_db()

        failure = False

        collection_names = [d._get_collection_name() for d in _document_registry.values()]

        for new_style_name in collection_names:
            if not new_style_name:  # embedded documents don't have collections
                continue
            old_style_name = new_style_name.replace('_', '')

            if old_style_name == new_style_name:
                continue  # Nothing to do

            existing = db.collection_names()
            if old_style_name in existing:
                if new_style_name in existing:
                    failure = True
                    print "FAILED to rename: %s to %s (already exists)" % (
                        old_style_name, new_style_name)
                else:
                    db[old_style_name].rename(new_style_name)
                    print "Renamed:  %s to %s" % (old_style_name, new_style_name)

        if failure:
            print "Upgrading  collection names failed"
        else:
            print "Upgraded collection names"

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