161 lines
5.6 KiB
Python
161 lines
5.6 KiB
Python
from collections import OrderedDict
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from cqlengine import columns
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from cqlengine.exceptions import ModelException
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from cqlengine.query import QuerySet
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class ModelDefinitionException(ModelException): pass
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class BaseModel(object):
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"""
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The base model class, don't inherit from this, inherit from Model, defined below
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"""
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#table names will be generated automatically from it's model and package name
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#however, you can alse define them manually here
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db_name = None
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#the keyspace for this model
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keyspace = 'cqlengine'
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def __init__(self, **values):
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self._values = {}
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for name, column in self._columns.items():
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value = values.get(name, None)
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if value is not None: value = column.to_python(value)
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value_mngr = column.value_manager(self, column, value)
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self._values[name] = value_mngr
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@classmethod
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def column_family_name(cls, include_keyspace=True):
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"""
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Returns the column family name if it's been defined
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otherwise, it creates it from the module and class name
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"""
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if cls.db_name:
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return cls.db_name.lower()
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cf_name = cls.__module__ + '.' + cls.__name__
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cf_name = cf_name.replace('.', '_')
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#trim to less than 48 characters or cassandra will complain
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cf_name = cf_name[-48:]
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cf_name = cf_name.lower()
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if not include_keyspace: return cf_name
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return '{}.{}'.format(cls.keyspace, cf_name)
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@property
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def pk(self):
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""" Returns the object's primary key """
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return getattr(self, self._pk_name)
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def validate(self):
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""" Cleans and validates the field values """
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for name, col in self._columns.items():
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val = col.validate(getattr(self, name))
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setattr(self, name, val)
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def as_dict(self):
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""" Returns a map of column names to cleaned values """
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values = self._dynamic_columns or {}
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for name, col in self._columns.items():
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values[name] = col.to_database(getattr(self, name, None))
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return values
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def save(self):
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is_new = self.pk is None
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self.validate()
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self.objects.save(self)
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#delete any fields that have been deleted / set to none
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return self
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def delete(self):
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""" Deletes this instance """
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self.objects.delete_instance(self)
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class ModelMetaClass(type):
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def __new__(cls, name, bases, attrs):
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"""
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"""
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#move column definitions into columns dict
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#and set default column names
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column_dict = OrderedDict()
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primary_keys = OrderedDict()
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pk_name = None
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def _transform_column(col_name, col_obj):
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column_dict[col_name] = col_obj
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if col_obj.primary_key:
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primary_keys[col_name] = col_obj
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col_obj.set_column_name(col_name)
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#set properties
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_get = lambda self: self._values[col_name].getval()
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_set = lambda self, val: self._values[col_name].setval(val)
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_del = lambda self: self._values[col_name].delval()
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if col_obj.can_delete:
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attrs[col_name] = property(_get, _set)
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else:
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attrs[col_name] = property(_get, _set, _del)
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column_definitions = [(k,v) for k,v in attrs.items() if isinstance(v, columns.Column)]
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column_definitions = sorted(column_definitions, lambda x,y: cmp(x[1].position, y[1].position))
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#prepend primary key if none has been defined
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if not any([v.primary_key for k,v in column_definitions]):
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k,v = 'id', columns.UUID(primary_key=True)
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column_definitions = [(k,v)] + column_definitions
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#TODO: check that the defined columns don't conflict with any of the Model API's existing attributes/methods
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#transform column definitions
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for k,v in column_definitions:
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if pk_name is None and v.primary_key:
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pk_name = k
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_transform_column(k,v)
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#setup primary key shortcut
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if pk_name != 'pk':
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attrs['pk'] = attrs[pk_name]
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#check for duplicate column names
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col_names = set()
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for v in column_dict.values():
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if v.db_field_name in col_names:
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raise ModelException("{} defines the column {} more than once".format(name, v.db_field_name))
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col_names.add(v.db_field_name)
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#check for indexes on models with multiple primary keys
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if len([1 for k,v in column_definitions if v.primary_key]) > 1:
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if len([1 for k,v in column_definitions if v.index]) > 0:
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raise ModelDefinitionException(
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'Indexes on models with multiple primary keys is not supported')
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#get column family name
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cf_name = attrs.pop('db_name', name)
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#create db_name -> model name map for loading
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db_map = {}
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for field_name, col in column_dict.items():
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db_map[col.db_field_name] = field_name
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#add management members to the class
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attrs['_columns'] = column_dict
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attrs['_primary_keys'] = primary_keys
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attrs['_db_map'] = db_map
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attrs['_pk_name'] = pk_name
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attrs['_dynamic_columns'] = {}
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#create the class and add a QuerySet to it
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klass = super(ModelMetaClass, cls).__new__(cls, name, bases, attrs)
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klass.objects = QuerySet(klass)
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return klass
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class Model(BaseModel):
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"""
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the db name for the column family can be set as the attribute db_name, or
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it will be genertaed from the class name
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"""
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__metaclass__ = ModelMetaClass
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