489 lines
17 KiB
Python
489 lines
17 KiB
Python
from django.apps import apps
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from django.core.cache import cache, caches
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class CollectionElement:
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@classmethod
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def from_instance(cls, instance, deleted=False, information=None):
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"""
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Returns a collection element from a database instance.
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This will also update the instance in the cache.
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If deleted is set to True, the element is deleted from the cache.
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"""
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return cls(instance=instance, deleted=deleted, information=information)
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@classmethod
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def from_values(cls, collection_string, id, deleted=False, full_data=None, information=None):
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"""
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Returns a collection element from a collection_string and an id.
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If deleted is set to True, the element is deleted from the cache.
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With the argument full_data, the content of the CollectionElement can be set.
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It has to be a dict in the format that is used be access_permission.get_full_data().
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"""
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return cls(collection_string=collection_string, id=id, deleted=deleted,
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full_data=full_data, information=information)
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def __init__(self, instance=None, deleted=False, collection_string=None, id=None,
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full_data=None, information=None):
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"""
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Do not use this. Use the methods from_instance() or from_values().
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"""
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self.instance = instance
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self.deleted = deleted
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self.full_data = full_data
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self.information = information or {}
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if instance is not None:
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self.collection_string = instance.get_collection_string()
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from openslides.core.config import config
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if self.collection_string == config.get_collection_string():
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# For config objects we do not work with the pk but with the key.
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self.id = instance.key
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else:
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self.id = instance.pk
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elif collection_string is not None and id is not None:
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self.collection_string = collection_string
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self.id = id
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else:
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raise RuntimeError(
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'Invalid state. Use CollectionElement.from_instance() or '
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'CollectionElement.from_values() but not CollectionElement() '
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'directly.')
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if self.is_deleted():
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# Delete the element from the cache, if self.is_deleted() is True:
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self.delete_from_cache()
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elif instance is not None:
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# If this element is created via instance and the instance is not deleted
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# then update the cache.
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self.save_to_cache()
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def __eq__(self, collection_element):
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"""
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Compares two collection_elements.
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Two collection elements are equal, if they have the same collection_string
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and id.
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"""
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return (self.collection_string == collection_element.collection_string and
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self.id == collection_element.id)
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def as_channels_message(self):
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"""
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Returns a dictonary that can be used to send the object through the
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channels system.
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"""
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channel_message = {
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'collection_string': self.collection_string,
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'id': self.id,
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'deleted': self.is_deleted()}
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if self.information is not None:
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channel_message['information'] = self.information
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return channel_message
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def as_autoupdate(self, method, *args):
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"""
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Only for internal use. Do not use it directly. Use as_autoupdate_for_user()
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or as_autoupdate_for_projector().
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"""
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output = {
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'collection': self.collection_string,
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'id': self.id,
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'action': 'deleted' if self.is_deleted() else 'changed',
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}
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if not self.is_deleted():
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data = getattr(self.get_access_permissions(), method)(
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self.get_full_data(),
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*args)
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if data is None:
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# The user is not allowed to see this element. Set action to deleted.
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output['action'] = 'deleted'
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else:
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output['data'] = data
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return output
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def as_autoupdate_for_user(self, user):
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"""
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Returns a dict that can be sent through the autoupdate system for a site
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user.
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"""
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return self.as_autoupdate(
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'get_restricted_data',
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user)
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def as_autoupdate_for_projector(self):
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"""
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Returns a dict that can be sent through the autoupdate system for the
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projector.
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"""
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return self.as_autoupdate(
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'get_projector_data')
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def as_dict_for_user(self, user):
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"""
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Returns a dict with the data for a user. Can be used for the rest api.
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"""
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return self.get_access_permissions().get_restricted_data(
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self.get_full_data(),
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user)
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def get_model(self):
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"""
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Returns the django model that is used for this collection.
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"""
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return get_model_from_collection_string(self.collection_string)
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def get_instance(self):
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"""
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Returns the instance as django object.
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May raise a DoesNotExist exception.
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"""
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if self.is_deleted():
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raise RuntimeError("The collection element is deleted.")
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if self.instance is None:
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# The config instance has to be get from the config element, because
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# some config values are not in the db.
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from openslides.core.config import config
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if self.collection_string == config.get_collection_string():
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self.instance = {'key': self.id, 'value': config[self.id]}
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else:
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model = self.get_model()
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try:
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query = model.objects.get_full_queryset()
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except AttributeError:
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query = model.objects
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self.instance = query.get(pk=self.id)
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return self.instance
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def get_access_permissions(self):
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"""
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Returns the get_access_permissions object for the this collection element.
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"""
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return self.get_model().get_access_permissions()
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def get_full_data(self):
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"""
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Returns the full_data of this collection_element from with all other
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dics can be generated.
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"""
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# If the full_data is already loaded, return it
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# If there is a db_instance, use it to get the full_data
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# else: try to use the cache.
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# If there is no value in the cach, get the content from the db and save
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# it to the cache.
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if self.full_data is None and self.instance is None:
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# Use the cache version if self.instance is not set.
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# After this line full_data can be None, if the element is not in the cache.
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self.full_data = cache.get(self.get_cache_key())
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if self.full_data is None:
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self.full_data = self.get_access_permissions().get_full_data(self.get_instance())
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self.save_to_cache()
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return self.full_data
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def is_deleted(self):
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"""
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Returns Ture if the item is marked as deleted.
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"""
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return self.deleted
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def get_cache_key(self):
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"""
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Returns a string that is used as cache key for a single instance.
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"""
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return get_single_element_cache_key(self.collection_string, self.id)
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def delete_from_cache(self):
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"""
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Delets an element from the cache.
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Does nothing if the element is not in the cache.
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"""
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# Deletes the element from the cache.
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cache.delete(self.get_cache_key())
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# Delete the id of the instance of the instance list
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Collection(self.collection_string).delete_id_from_cache(self.id)
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def save_to_cache(self):
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"""
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Add or update the element to the cache.
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"""
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# Set the element to the cache.
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cache.set(self.get_cache_key(), self.get_full_data())
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# Add the id of the element to the collection
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Collection(self.collection_string).add_id_to_cache(self.id)
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class Collection:
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"""
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Represents all elements of one collection.
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"""
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def __init__(self, collection_string):
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self.collection_string = collection_string
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def get_cache_key(self, raw=False):
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"""
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Returns a string that is used as cache key for a collection.
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Django adds a prefix to the cache key when using the django cache api.
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In other cases use raw=True to add the same cache key.
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"""
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key = get_element_list_cache_key(self.collection_string)
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if raw:
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key = cache.make_key(key)
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return key
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def get_model(self):
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"""
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Returns the django model that is used for this collection.
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"""
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return get_model_from_collection_string(self.collection_string)
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def element_generator(self):
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"""
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Generator that yields all collection_elements of this collection.
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"""
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# Get all cache keys.
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ids = self.get_all_ids()
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cache_keys = [
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get_single_element_cache_key(self.collection_string, id)
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for id in ids]
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cached_full_data_dict = cache.get_many(cache_keys)
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# Get all ids that are missing.
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missing_ids = set()
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for cache_key in cache_keys:
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if cache_key not in cached_full_data_dict:
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missing_ids.add(get_collection_id_from_cache_key(cache_key)[1])
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# Generate collection elements that where in the cache.
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for cache_key, cached_full_data in cached_full_data_dict.items():
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yield CollectionElement.from_values(
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*get_collection_id_from_cache_key(cache_key),
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full_data=cached_full_data)
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# Generate collection element that where not in the cache.
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if missing_ids:
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from openslides.core.config import config
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if self.collection_string == config.get_collection_string():
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# If config elements are not in the cache, they have to be read from
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# the config object.
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for key, value in config.items():
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if key in missing_ids:
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collection_element = CollectionElement.from_values(
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config.get_collection_string(),
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key,
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full_data={'key': key, 'value': value})
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# We can not use .from_instance therefore the config value
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# is not saved to the cache. We have to do it manualy.
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collection_element.save_to_cache()
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yield collection_element
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else:
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model = self.get_model()
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try:
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query = model.objects.get_full_queryset()
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except AttributeError:
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query = model.objects
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for instance in query.filter(pk__in=missing_ids):
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yield CollectionElement.from_instance(instance)
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def as_autoupdate_for_projector(self):
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"""
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Returns a list of dictonaries to send them to the projector.
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"""
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output = []
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for collection_element in self.element_generator():
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content = collection_element.as_autoupdate_for_projector()
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# Content can not be None. If the projector can not see an element,
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# then it is marked as deleted.
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output.append(content)
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return output
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def as_list_for_user(self, user):
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"""
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Returns a list of dictonaries to send them to a user, for example over
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the rest api.
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"""
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output = []
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for collection_element in self.element_generator():
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content = collection_element.as_dict_for_user(user)
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if content is not None:
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output.append(content)
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return output
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def get_all_ids(self):
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"""
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Returns a set of all ids of instances in this collection.
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"""
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from openslides.core.config import config
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if self.collection_string == config.get_collection_string():
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ids = config.config_variables.keys()
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elif use_redis_cache():
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ids = self.get_all_ids_redis()
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else:
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ids = self.get_all_ids_other()
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return ids
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def get_all_ids_redis(self):
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redis = get_redis_connection()
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ids = redis.smembers(self.get_cache_key(raw=True))
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if not ids:
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ids = set(self.get_model().objects.values_list('pk', flat=True))
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if ids:
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redis.sadd(self.get_cache_key(raw=True), *ids)
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# Redis returns the ids as string.
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ids = set(int(id) for id in ids)
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return ids
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def get_all_ids_other(self):
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ids = cache.get(self.get_cache_key())
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if ids is None:
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# If it is not in the cache then get it from the database.
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ids = set(self.get_model().objects.values_list('pk', flat=True))
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cache.set(self.get_cache_key(), ids)
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return ids
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def delete_id_from_cache(self, id):
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"""
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Delets a id from the cache.
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"""
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if use_redis_cache():
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self.delete_id_from_cache_redis(id)
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else:
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self.delete_id_from_cache_other(id)
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def delete_id_from_cache_redis(self, id):
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redis = get_redis_connection()
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redis.srem(self.get_cache_key(raw=True), id)
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def delete_id_from_cache_other(self, id):
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ids = cache.get(self.get_cache_key())
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if ids is not None:
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ids = set(ids)
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try:
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ids.remove(id)
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except KeyError:
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# The id is not part of id list
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pass
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else:
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if ids:
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cache.set(self.get_cache_key(), ids)
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else:
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# Delete the key, if there are not ids left
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cache.delete(self.get_cache_key())
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def add_id_to_cache(self, id):
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"""
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Adds a collection id to the list of collection ids in the cache.
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"""
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if use_redis_cache():
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self.add_id_to_cache_redis(id)
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else:
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self.add_id_to_cache_other(id)
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def add_id_to_cache_redis(self, id):
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redis = get_redis_connection()
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if redis.exists(self.get_cache_key(raw=True)):
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# Only add the value if it is in the cache.
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redis.sadd(self.get_cache_key(raw=True), id)
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def add_id_to_cache_other(self, id):
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ids = cache.get(self.get_cache_key())
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if ids is not None:
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# Only change the value if it is in the cache.
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ids = set(ids)
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ids.add(id)
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cache.set(self.get_cache_key(), ids)
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def get_model_from_collection_string(collection_string):
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"""
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Returns a model class which belongs to the argument collection_string.
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"""
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def model_generator():
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"""
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Yields all models of all apps.
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"""
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for app_config in apps.get_app_configs():
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for model in app_config.get_models():
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yield model
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for model in model_generator():
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try:
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model_collection_string = model.get_collection_string()
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except AttributeError:
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# Skip models which do not have the method get_collection_string.
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pass
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else:
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if model_collection_string == collection_string:
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# The model was found.
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break
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else:
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# No model was found in all apps.
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raise ValueError('Invalid message. A valid collection_string is missing.')
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return model
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def get_single_element_cache_key(collection_string, id):
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"""
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Returns a string that is used as cache key for a single instance.
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"""
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return "{prefix}{id}".format(
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prefix=get_single_element_cache_key_prefix(collection_string),
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id=id)
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def get_single_element_cache_key_prefix(collection_string):
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"""
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Returns the first part of the cache key for single elements, which is the
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same for all cache keys of the same collection.
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"""
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return "{collection}:".format(collection=collection_string)
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def get_element_list_cache_key(collection_string):
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"""
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Returns a string that is used as cache key for a collection.
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"""
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return "{collection}".format(collection=collection_string)
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def get_collection_id_from_cache_key(cache_key):
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"""
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Returns a tuble of the collection string and the id from a cache_key
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created with get_instance_cache_key.
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The returned id can be an integer or an string.
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"""
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collection_string, id = cache_key.rsplit(':', 1)
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try:
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id = int(id)
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except ValueError:
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# The id is no integer. This can happen on config elements
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pass
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return (collection_string, id)
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def use_redis_cache():
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"""
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Returns True if Redis is used als caching backend.
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"""
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try:
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from django_redis.cache import RedisCache
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except ImportError:
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return False
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return isinstance(caches['default'], RedisCache)
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def get_redis_connection():
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from django_redis import get_redis_connection
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return get_redis_connection("default")
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