def _discover_polymorphic_submodels(cls):
if not cls._is_polymorphic_base:
raise ModelException(
'_discover_polymorphic_submodels can only be called on polymorphic base classes'
)
def _discover(klass):
if not klass._is_polymorphic_base and klass.__polymorphic_key__ is not None:
cls._polymorphic_map[klass.__polymorphic_key__] = klass
for subklass in klass.__subclasses__():
_discover(subklass)
_discover(cls)
def __new__(cls, name, bases, attrs):
"""
"""
#move column definitions into columns dict
#and set default column names
column_dict = OrderedDict()
primary_keys = OrderedDict()
pk_name = None
#get inherited properties
inherited_columns = OrderedDict()
for base in bases:
for k, v in getattr(base, '_defined_columns', {}).items():
inherited_columns.setdefault(k, v)
#short circuit __abstract__ inheritance
is_abstract = attrs['__abstract__'] = attrs.get('__abstract__', False)
#short circuit __polymorphic_key__ inheritance
attrs['__polymorphic_key__'] = attrs.get('__polymorphic_key__', None)
def _transform_column(col_name, col_obj):
column_dict[col_name] = col_obj
if col_obj.primary_key:
primary_keys[col_name] = col_obj
col_obj.set_column_name(col_name)
#set properties
attrs[col_name] = ColumnDescriptor(col_obj)
column_definitions = [(k, v) for k, v in attrs.items()
if isinstance(v, columns.Column)]
#column_definitions = sorted(column_definitions, lambda x,y: cmp(x[1].position, y[1].position))
column_definitions = sorted(column_definitions,
key=lambda x: x[1].position)
is_polymorphic_base = any(
[c[1].polymorphic_key for c in column_definitions])
column_definitions = [x for x in inherited_columns.items()
] + column_definitions
polymorphic_columns = [
c for c in column_definitions if c[1].polymorphic_key
]
is_polymorphic = len(polymorphic_columns) > 0
if len(polymorphic_columns) > 1:
raise ModelDefinitionException(
'only one polymorphic_key can be defined in a model, {} found'.
format(len(polymorphic_columns)))
polymorphic_column_name, polymorphic_column = polymorphic_columns[
0] if polymorphic_columns else (None, None)
if isinstance(polymorphic_column,
(columns.BaseContainerColumn, columns.Counter)):
raise ModelDefinitionException(
'counter and container columns cannot be used for polymorphic keys'
)
# find polymorphic base class
polymorphic_base = None
if is_polymorphic and not is_polymorphic_base:
def _get_polymorphic_base(bases):
for base in bases:
if getattr(base, '_is_polymorphic_base', False):
return base
klass = _get_polymorphic_base(base.__bases__)
if klass:
return klass
polymorphic_base = _get_polymorphic_base(bases)
defined_columns = OrderedDict(column_definitions)
# check for primary key
if not is_abstract and not any(
[v.primary_key for k, v in column_definitions]):
raise ModelDefinitionException(
"At least 1 primary key is required.")
counter_columns = [
c for c in defined_columns.values()
if isinstance(c, columns.Counter)
]
data_columns = [
c for c in defined_columns.values()
if not c.primary_key and not isinstance(c, columns.Counter)
]
if counter_columns and data_columns:
raise ModelDefinitionException(
'counter models may not have data columns')
has_partition_keys = any(v.partition_key
for (k, v) in column_definitions)
#transform column definitions
for k, v in column_definitions:
# don't allow a column with the same name as a built-in attribute or method
if k in BaseModel.__dict__:
raise ModelDefinitionException(
"column '{}' conflicts with built-in attribute/method".
format(k))
# counter column primary keys are not allowed
if (v.primary_key or v.partition_key) and isinstance(
v, (columns.Counter, columns.BaseContainerColumn)):
raise ModelDefinitionException(
'counter columns and container columns cannot be used as primary keys'
)
# this will mark the first primary key column as a partition
# key, if one hasn't been set already
if not has_partition_keys and v.primary_key:
v.partition_key = True
has_partition_keys = True
_transform_column(k, v)
partition_keys = OrderedDict(k for k in primary_keys.items()
if k[1].partition_key)
clustering_keys = OrderedDict(k for k in primary_keys.items()
if not k[1].partition_key)
#setup partition key shortcut
if len(partition_keys) == 0:
if not is_abstract:
raise ModelException(
"at least one partition key must be defined")
if len(partition_keys) == 1:
pk_name = [x for x in partition_keys.keys()][0]
attrs['pk'] = attrs[pk_name]
else:
# composite partition key case, get/set a tuple of values
_get = lambda self: tuple(self._values[c].getval()
for c in partition_keys.keys())
_set = lambda self, val: tuple(self._values[c].setval(v)
for (c, v) in zip(
partition_keys.keys(), val))
attrs['pk'] = property(_get, _set)
# some validation
col_names = set()
for v in column_dict.values():
# check for duplicate column names
if v.db_field_name in col_names:
raise ModelException(
"{} defines the column {} more than once".format(
name, v.db_field_name))
if v.clustering_order and not (v.primary_key
and not v.partition_key):
raise ModelException(
"clustering_order may be specified only for clustering primary keys"
)
if v.clustering_order and v.clustering_order.lower() not in (
'asc', 'desc'):
raise ModelException(
"invalid clustering order {} for column {}".format(
repr(v.clustering_order), v.db_field_name))
col_names.add(v.db_field_name)
#create db_name -> model name map for loading
db_map = {}
for field_name, col in column_dict.items():
db_map[col.db_field_name] = field_name
#add management members to the class
attrs['_columns'] = column_dict
attrs['_primary_keys'] = primary_keys
attrs['_defined_columns'] = defined_columns
# maps the database field to the models key
attrs['_db_map'] = db_map
attrs['_pk_name'] = pk_name
attrs['_dynamic_columns'] = {}
attrs['_partition_keys'] = partition_keys
attrs['_clustering_keys'] = clustering_keys
attrs['_has_counter'] = len(counter_columns) > 0
# add polymorphic management attributes
attrs['_is_polymorphic_base'] = is_polymorphic_base
attrs['_is_polymorphic'] = is_polymorphic
attrs['_polymorphic_base'] = polymorphic_base
attrs['_polymorphic_column'] = polymorphic_column
attrs['_polymorphic_column_name'] = polymorphic_column_name
attrs['_polymorphic_map'] = {} if is_polymorphic_base else None
#setup class exceptions
DoesNotExistBase = None
for base in bases:
DoesNotExistBase = getattr(base, 'DoesNotExist', None)
if DoesNotExistBase is not None: break
DoesNotExistBase = DoesNotExistBase or attrs.pop(
'DoesNotExist', BaseModel.DoesNotExist)
attrs['DoesNotExist'] = type('DoesNotExist', (DoesNotExistBase, ), {})
MultipleObjectsReturnedBase = None
for base in bases:
MultipleObjectsReturnedBase = getattr(base,
'MultipleObjectsReturned',
None)
if MultipleObjectsReturnedBase is not None: break
MultipleObjectsReturnedBase = DoesNotExistBase or attrs.pop(
'MultipleObjectsReturned', BaseModel.MultipleObjectsReturned)
attrs['MultipleObjectsReturned'] = type(
'MultipleObjectsReturned', (MultipleObjectsReturnedBase, ), {})
#create the class and add a QuerySet to it
klass = super(ModelMetaClass, cls).__new__(cls, name, bases, attrs)
return klass
def _get_model_by_polymorphic_key(cls, key):
if not cls._is_polymorphic_base:
raise ModelException(
'_get_model_by_polymorphic_key can only be called on polymorphic base classes'
)
return cls._polymorphic_map.get(key)