bc30addfb9
fixing unit tests fixing merge error fixing xqueue submission issue with unicode url (trial 0.1) fixing fotmats as commented upon removing yaml file language selection Unicode changes to support QRF removed unnecessary pass in modulestore/init.py fixing merge error fixing fotmats as commented upon removing yaml file language selection fixing pep8 violations - fixing pylint violations pylint violation fixing line spaces and formats ignore pylint E1101 remove empty line fixing pylint violations pep8 violations bulk mail unicode/decode fix migration error fix pep8 just to push again more unicode/decode Final changes to comments and error messages.
122 lines
3.5 KiB
Python
122 lines
3.5 KiB
Python
"""
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Core methods
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------------
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.. autofunction:: cache_toolbox.core.get_instance
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.. autofunction:: cache_toolbox.core.delete_instance
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.. autofunction:: cache_toolbox.core.instance_key
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"""
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from django.core.cache import cache
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from django.db import DEFAULT_DB_ALIAS
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from . import app_settings
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def get_instance(model, instance_or_pk, timeout=None, using=None):
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"""
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Returns the ``model`` instance with a primary key of ``instance_or_pk``.
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If the data is cached it will be returned from there, otherwise the regular
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Django ORM is queried for this instance and the data stored in the cache.
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If omitted, the timeout value defaults to
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``settings.CACHE_TOOLBOX_DEFAULT_TIMEOUT`` instead of 0 (zero).
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Example::
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>>> get_instance(User, 1) # Cache miss
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<User: lamby>
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>>> get_instance(User, 1) # Cache hit
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<User: lamby>
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>>> User.objects.get(pk=1) == get_instance(User, 1)
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True
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"""
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pk = getattr(instance_or_pk, 'pk', instance_or_pk)
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key = instance_key(model, instance_or_pk)
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data = cache.get(key)
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if data is not None:
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try:
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# Try and construct instance from dictionary
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instance = model(pk=pk, **data)
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# Ensure instance knows that it already exists in the database,
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# otherwise we will fail any uniqueness checks when saving the
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# instance.
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instance._state.adding = False
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# Specify database so that instance is setup correctly. We don't
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# namespace cached objects by their origin database, however.
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instance._state.db = using or DEFAULT_DB_ALIAS
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return instance
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except:
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# Error when deserialising - remove from the cache; we will
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# fallback and return the underlying instance
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cache.delete(key)
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# Use the default manager so we are never filtered by a .get_query_set()
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# import logging
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# log = logging.getLogger("tracking")
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# log.info( str(pk) )
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instance = model._default_manager.using(using).get(pk=pk)
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data = {}
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for field in instance._meta.fields:
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# Harmless to save, but saves space in the dictionary - we already know
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# the primary key when we lookup
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if field.primary_key:
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continue
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if field.get_internal_type() == 'FileField':
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# Avoid problems with serializing FileFields
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# by only serializing the file name
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file = getattr(instance, field.attname)
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data[field.attname] = file.name
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else:
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data[field.attname] = getattr(instance, field.attname)
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if timeout is None:
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timeout = app_settings.CACHE_TOOLBOX_DEFAULT_TIMEOUT
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cache.set(key, data, timeout)
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return instance
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def delete_instance(model, *instance_or_pk):
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"""
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Purges the cache keys for the instances of this model.
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"""
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cache.delete_many([instance_key(model, x) for x in instance_or_pk])
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def instance_key(model, instance_or_pk):
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"""
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Returns the cache key for this (model, instance) pair.
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"""
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return '%s.%s:%d' % (
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model._meta.app_label,
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model._meta.module_name,
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getattr(instance_or_pk, 'pk', instance_or_pk),
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)
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def set_cached_content(content):
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cache.set(unicode(content.location).encode("utf-8"), content)
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def get_cached_content(location):
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return cache.get(unicode(location).encode("utf-8"))
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def del_cached_content(location):
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cache.delete(unicode(location).encode("utf-8"))
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