def allow_relation(self, obj1, obj2, **hints):
"""
Only allow relationships between two items which are both on only one database or
between sharded items on the same shard.
"""
object1_databases = get_possible_databases_for_model(model=obj1._meta.model)
object2_databases = get_possible_databases_for_model(model=obj2._meta.model)
if (len(object1_databases) == len(object2_databases) == 1) and (object1_databases == object2_databases):
return True
return self.get_shard_for_instance(obj1) == self.get_shard_for_instance(obj2)
def allow_relation(self, obj1, obj2, **hints):
"""
Only allow relationships between two items which are both on only one database or
between sharded items on the same shard.
"""
object1_databases = get_possible_databases_for_model(model=obj1._meta.model)
object2_databases = get_possible_databases_for_model(model=obj2._meta.model)
if (len(object1_databases) == len(object2_databases) == 1) and (object1_databases == object2_databases):
return True
return self.get_shard_for_instance(obj1) == self.get_shard_for_instance(obj2)
def db_for_write(self, model, **hints):
possible_databases = get_possible_databases_for_model(model=model)
if len(possible_databases) == 1:
return possible_databases[0]
shard = self._get_shard(model, **hints)
if shard:
db_config = settings.DATABASES[shard]
return db_config.get('PRIMARY', shard)
return None
def db_for_write(self, model, **hints):
possible_databases = get_possible_databases_for_model(model=model)
if len(possible_databases) == 1:
return possible_databases[0]
shard = self._get_shard(model, **hints)
if shard:
db_config = settings.DATABASES[shard]
return db_config.get('PRIMARY', shard)
return None
def get_shards(model):
"""
Get shards(only primary db).
"""
shards = []
for s in get_possible_databases_for_model(model):
db_config = settings.DATABASES[s]
if db_config.get('PRIMARY') is None:
shards.append(s)
return shards
def db_for_read(self, model, **hints):
possible_databases = get_possible_databases_for_model(model=model)
if len(possible_databases) == 1:
return possible_databases[0]
shard = self._get_shard(model, **hints)
if shard:
shard_group = getattr(model, 'django_sharding__shard_group', None)
if not shard_group:
raise DjangoShardingException('Unable to identify the shard_group for the {} model'.format(model))
routing_strategy = self.get_read_db_routing_strategy(shard_group)
return routing_strategy.pick_read_db(shard)
return None
def db_for_read(self, model, **hints):
possible_databases = get_possible_databases_for_model(model=model)
if len(possible_databases) == 1:
return possible_databases[0]
shard = self._get_shard(model, **hints)
if shard:
shard_group = getattr(model, 'django_sharding__shard_group', None)
if not shard_group:
raise DjangoShardingException('Unable to identify the shard_group for the {} model'.format(model))
routing_strategy = self.get_read_db_routing_strategy(shard_group)
return routing_strategy.pick_read_db(shard)
return None
