author | Nishanth Amuluru <nishanth@fossee.in> |
Tue, 11 Jan 2011 12:36:55 +0530 | |
changeset 141 | ed2dadfc829a |
parent 69 | c6bca38c1cbf |
permissions | -rw-r--r-- |
69
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
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from django.contrib.contenttypes.models import ContentType |
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def fetch_content_objects(tagged_items, select_related_for=None): |
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""" |
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Retrieves ``ContentType`` and content objects for the given list of |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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``TaggedItems``, grouping the retrieval of content objects by model |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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type to reduce the number of queries executed. |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
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Nishanth Amuluru <nishanth@fossee.in>
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This results in ``number_of_content_types + 1`` queries rather than |
c6bca38c1cbf
Added buildout stuff and made changes accordingly
Nishanth Amuluru <nishanth@fossee.in>
parents:
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the ``number_of_tagged_items * 2`` queries you'd get by iterating |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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over the list and accessing each item's ``object`` attribute. |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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|
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Nishanth Amuluru <nishanth@fossee.in>
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A ``select_related_for`` argument can be used to specify a list of |
c6bca38c1cbf
Added buildout stuff and made changes accordingly
Nishanth Amuluru <nishanth@fossee.in>
parents:
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of model names (corresponding to the ``model`` field of a |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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``ContentType``) for which ``select_related`` should be used when |
c6bca38c1cbf
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Nishanth Amuluru <nishanth@fossee.in>
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retrieving model instances. |
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Nishanth Amuluru <nishanth@fossee.in>
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""" |
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if select_related_for is None: select_related_for = [] |
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# Group content object pks by their content type pks |
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objects = {} |
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for item in tagged_items: |
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objects.setdefault(item.content_type_id, []).append(item.object_id) |
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|
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# Retrieve content types and content objects in bulk |
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content_types = ContentType._default_manager.in_bulk(objects.keys()) |
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for content_type_pk, object_pks in objects.iteritems(): |
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model = content_types[content_type_pk].model_class() |
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if content_types[content_type_pk].model in select_related_for: |
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objects[content_type_pk] = model._default_manager.select_related().in_bulk(object_pks) |
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else: |
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objects[content_type_pk] = model._default_manager.in_bulk(object_pks) |
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|
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# Set content types and content objects in the appropriate cache |
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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# attributes, so accessing the 'content_type' and 'object' |
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Nishanth Amuluru <nishanth@fossee.in>
parents:
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# attributes on each tagged item won't result in further database |
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Nishanth Amuluru <nishanth@fossee.in>
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# hits. |
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for item in tagged_items: |
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item._object_cache = objects[item.content_type_id][item.object_id] |
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item._content_type_cache = content_types[item.content_type_id] |