# -*- coding: utf-8 -*-
import logging
import uuid
import django
from django.db.models.signals import post_save, post_delete, m2m_changed
from django.db.models.fields.related import RelatedField
from .model_cache_sharing.types import ModelCacheInfo
from .model_cache_sharing import model_cache_backend
"""
Signal receivers for django model post_save and post_delete. Used to evict a model cache when
an update or delete happens on the model.
For compatibility with Django 1.5 these receivers live in models.py
"""
logger = logging.getLogger(__name__)
def update_model_cache(table_name):
"""
Updates model cache by generating a new key for the model
"""
model_cache_info = ModelCacheInfo(table_name, uuid.uuid4().hex)
model_cache_backend.share_model_cache_info(model_cache_info)
def invalidate_model_cache(sender, instance, **kwargs):
"""
Signal receiver for models to invalidate model cache of sender and related models.
Model cache is invalidated by generating new key for each model.
Parameters
~~~~~~~~~~
sender
The model class
instance
The actual instance being saved.
"""
logger.debug('Received post_save/post_delete signal from sender {0}'.format(sender))
if django.VERSION >= (1, 8):
related_tables = set(
[f.related_model._meta.db_table for f in sender._meta.get_fields()
if f.related_model is not None
and (((f.one_to_many or f.one_to_one) and f.auto_created)
or f.many_to_one or (f.many_to_many and not f.auto_created))])
else:
related_tables = set([rel.model._meta.db_table for rel in sender._meta.get_all_related_objects()])
# temporary fix for m2m relations with an intermediate model, goes away after better join caching
related_tables |= set([field.rel.to._meta.db_table for field in sender._meta.fields if issubclass(type(field), RelatedField)])
logger.debug('Related tables of sender {0} are {1}'.format(sender, related_tables))
update_model_cache(sender._meta.db_table)
for related_table in related_tables:
update_model_cache(related_table)
def invalidate_m2m_cache(sender, instance, model, **kwargs):
"""
Signal receiver for models to invalidate model cache for many-to-many relationship.
Parameters
~~~~~~~~~~
sender
The model class
instance
The instance whose many-to-many relation is updated.
model
The class of the objects that are added to, removed from or cleared from the relation.
"""
logger.debug('Received m2m_changed signals from sender {0}'.format(sender))
update_model_cache(instance._meta.db_table)
update_model_cache(model._meta.db_table)
post_save.connect(invalidate_model_cache)
post_delete.connect(invalidate_model_cache)
m2m_changed.connect(invalidate_m2m_cache)
