84 lines
2.4 KiB
ReStructuredText
84 lines
2.4 KiB
ReStructuredText
======
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GridFS
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======
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.. versionadded:: 0.4
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Writing
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-------
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GridFS support comes in the form of the :class:`~mongoengine.FileField` field
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object. This field acts as a file-like object and provides a couple of
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different ways of inserting and retrieving data. Arbitrary metadata such as
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content type can also be stored alongside the files. In the following example,
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a document is created to store details about animals, including a photo::
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class Animal(Document):
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genus = StringField()
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family = StringField()
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photo = FileField()
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marmot = Animal('Marmota', 'Sciuridae')
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marmot_photo = open('marmot.jpg', 'r') # Retrieve a photo from disk
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marmot.photo = marmot_photo # Store photo in the document
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marmot.photo.content_type = 'image/jpeg' # Store metadata
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marmot.save()
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Another way of writing to a :class:`~mongoengine.FileField` is to use the
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:func:`put` method. This allows for metadata to be stored in the same call as
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the file::
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marmot.photo.put(marmot_photo, content_type='image/jpeg')
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marmot.save()
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Retrieval
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---------
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So using the :class:`~mongoengine.FileField` is just like using any other
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field. The file can also be retrieved just as easily::
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marmot = Animal.objects(genus='Marmota').first()
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photo = marmot.photo.read()
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content_type = marmot.photo.content_type
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Streaming
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---------
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Streaming data into a :class:`~mongoengine.FileField` is achieved in a
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slightly different manner. First, a new file must be created by calling the
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:func:`new_file` method. Data can then be written using :func:`write`::
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marmot.photo.new_file()
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marmot.photo.write('some_image_data')
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marmot.photo.write('some_more_image_data')
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marmot.photo.close()
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marmot.photo.save()
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Deletion
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--------
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Deleting stored files is achieved with the :func:`delete` method::
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marmot.photo.delete()
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.. note::
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The FileField in a Document actually only stores the ID of a file in a
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separate GridFS collection. This means that `Animal.drop_collection()` will
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not delete any files. Care should be taken to manually remove associated
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files before dropping a collection.
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Replacing files
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---------------
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Files can be replaced with the :func:`replace` method. This works just like
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the :func:`put` method so even metadata can (and should) be replaced::
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another_marmot = open('another_marmot.png', 'r')
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marmot.photo.replace(another_marmot, content_type='image/png')
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