def random_assign(self):
"""Return a randomly-selected object from the QuerySet.
Requires that the QuerySet has been configured with an `assigned_object` field:
the objects' related model field to be assigned.
The objects' model must also have a `rand_cdf` field, the CDF probability of
the object.
"""
assigned_object = getattr(self, 'assigned_object', None)
if not assigned_object:
raise TypeError("Assigned object field not set")
assigned_object = getattr(assigned_object, 'name', assigned_object)
for field in self.model._meta.fields:
if field.name == assigned_object:
assigned_class = field.related.parent_model
break
else:
raise TypeError("Field {!r} not found on model {meta.app_label}.{meta.object_name}"
.format(assigned_object, meta=self.model._meta))
options = self.values_list(assigned_object, 'rand_cdf')
object_id = utils.random_assign(options)
return assigned_class.objects.get(pk=object_id)
def assign_page_styles(visit, page_code, campaign, content=None):
"""Randomly assign a set of stylesheets to the page for the given campaign,
and record that assignment.
Database results are cached according to the `PAGE_STYLE_CACHE_TIMEOUT` setting.
"""
# Look up PageStyles:
cache_key = 'campaignpagestylesets|{}|{}'.format(page_code, campaign.pk)
options = django.core.cache.cache.get(cache_key)
if options is None:
# Retrieve from DB:
campaign_page_style_sets = campaign.campaignpagestylesets.filter(
page_style_set__page_styles__page__code=page_code,
).values_list('pk', 'page_style_set_id', 'rand_cdf').distinct()
options = tuple(campaign_page_style_sets.iterator())
if options:
# Store in cache
django.core.cache.cache.set(cache_key, options, settings.PAGE_STYLE_CACHE_TIMEOUT)
# Assign PageStyles:
page_style_set_id = utils.random_assign(
(page_style_set_id, rand_cdf)
for (_pk, page_style_set_id, rand_cdf) in options
)
# Record assignment:
db.delayed_save.delay(
models.relational.Assignment.make_managed(
visit_id=visit.pk,
campaign_id=campaign.pk,
content_id=(content and content.pk),
feature_row=page_style_set_id,
chosen_from_rows=[pk for (pk, _page_style_set_id, _rand_cdf) in options],
manager=campaign.campaignpagestylesets,
)
)
cache_key = 'pagestyleset|{}'.format(page_style_set_id)
hrefs = django.core.cache.cache.get(cache_key)
if hrefs is None:
page_style_set = models.relational.PageStyleSet.objects.get(pk=page_style_set_id)
page_styles = page_style_set.page_styles.only('url')
hrefs = tuple(page_style.href for page_style in page_styles.iterator())
django.core.cache.cache.set(cache_key, hrefs, settings.PAGE_STYLE_CACHE_TIMEOUT)
return hrefs
