421 lines
14 KiB
Python
421 lines
14 KiB
Python
from collections import OrderedDict
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import re
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from cqlengine import columns
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from cqlengine.exceptions import ModelException, CQLEngineException, ValidationError
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from cqlengine.query import ModelQuerySet, DMLQuery, AbstractQueryableColumn
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from cqlengine.query import DoesNotExist as _DoesNotExist
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from cqlengine.query import MultipleObjectsReturned as _MultipleObjectsReturned
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class ModelDefinitionException(ModelException): pass
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DEFAULT_KEYSPACE = 'cqlengine'
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class hybrid_classmethod(object):
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"""
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Allows a method to behave as both a class method and
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normal instance method depending on how it's called
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"""
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def __init__(self, clsmethod, instmethod):
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self.clsmethod = clsmethod
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self.instmethod = instmethod
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def __get__(self, instance, owner):
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if instance is None:
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return self.clsmethod.__get__(owner, owner)
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else:
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return self.instmethod.__get__(instance, owner)
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def __call__(self, *args, **kwargs):
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"""
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Just a hint to IDEs that it's ok to call this
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"""
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raise NotImplementedError
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class QuerySetDescriptor(object):
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"""
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returns a fresh queryset for the given model
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it's declared on everytime it's accessed
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"""
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def __get__(self, obj, model):
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""" :rtype: ModelQuerySet """
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if model.__abstract__:
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raise CQLEngineException('cannot execute queries against abstract models')
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return ModelQuerySet(model)
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def __call__(self, *args, **kwargs):
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"""
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Just a hint to IDEs that it's ok to call this
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:rtype: ModelQuerySet
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"""
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raise NotImplementedError
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class ColumnQueryEvaluator(AbstractQueryableColumn):
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"""
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Wraps a column and allows it to be used in comparator
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expressions, returning query operators
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ie:
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Model.column == 5
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"""
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def __init__(self, column):
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self.column = column
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def _get_column(self):
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return self.column
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class ColumnDescriptor(object):
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"""
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Handles the reading and writing of column values to and from
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a model instance's value manager, as well as creating
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comparator queries
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"""
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def __init__(self, column):
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"""
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:param column:
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:type column: columns.Column
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:return:
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"""
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self.column = column
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self.query_evaluator = ColumnQueryEvaluator(self.column)
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def __get__(self, instance, owner):
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"""
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Returns either the value or column, depending
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on if an instance is provided or not
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:param instance: the model instance
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:type instance: Model
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"""
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if instance:
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return instance._values[self.column.column_name].getval()
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else:
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return self.query_evaluator
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def __set__(self, instance, value):
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"""
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Sets the value on an instance, raises an exception with classes
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TODO: use None instance to create update statements
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"""
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if instance:
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return instance._values[self.column.column_name].setval(value)
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else:
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raise AttributeError('cannot reassign column values')
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def __delete__(self, instance):
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"""
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Sets the column value to None, if possible
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"""
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if instance:
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if self.column.can_delete:
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instance._values[self.column.column_name].delval()
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else:
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raise AttributeError('cannot delete {} columns'.format(self.column.column_name))
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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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class DoesNotExist(_DoesNotExist): pass
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class MultipleObjectsReturned(_MultipleObjectsReturned): pass
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objects = QuerySetDescriptor()
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#table names will be generated automatically from it's model and package name
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#however, you can also define them manually here
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__table_name__ = None
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#the keyspace for this model
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__keyspace__ = None
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__read_repair_chance__ = 0.1
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def __init__(self, **values):
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self._values = {}
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extra_columns = set(values.keys()) - set(self._columns.keys())
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if extra_columns:
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raise ValidationError("Incorrect columns passed: {}".format(extra_columns))
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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 or isinstance(column, columns.BaseContainerColumn):
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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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# a flag set by the deserializer to indicate
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# that update should be used when persisting changes
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self._is_persisted = False
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self._batch = None
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def _can_update(self):
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"""
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Called by the save function to check if this should be
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persisted with update or insert
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:return:
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"""
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if not self._is_persisted: return False
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pks = self._primary_keys.keys()
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return all([not self._values[k].changed for k in self._primary_keys])
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@classmethod
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def _get_keyspace(cls):
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""" Returns the manual keyspace, if set, otherwise the default keyspace """
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return cls.__keyspace__ or DEFAULT_KEYSPACE
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@classmethod
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def _get_column(cls, name):
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"""
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Returns the column matching the given name, raising a key error if
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it doesn't exist
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:param name: the name of the column to return
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:rtype: Column
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"""
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return cls._columns[name]
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def __eq__(self, other):
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if self.__class__ != other.__class__:
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return False
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# check attribute keys
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keys = set(self._columns.keys())
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other_keys = set(self._columns.keys())
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if keys != other_keys:
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return False
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# check that all of the attributes match
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for key in other_keys:
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if getattr(self, key, None) != getattr(other, key, None):
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return False
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return True
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def __ne__(self, other):
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return not self.__eq__(other)
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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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cf_name = ''
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if cls.__table_name__:
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cf_name = cls.__table_name__.lower()
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else:
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camelcase = re.compile(r'([a-z])([A-Z])')
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ccase = lambda s: camelcase.sub(lambda v: '{}_{}'.format(v.group(1), v.group(2).lower()), s)
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cf_name += ccase(cls.__name__)
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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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cf_name = re.sub(r'^_+', '', cf_name)
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if not include_keyspace: return cf_name
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return '{}.{}'.format(cls._get_keyspace(), cf_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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@classmethod
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def create(cls, **kwargs):
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return cls.objects.create(**kwargs)
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@classmethod
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def all(cls):
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return cls.objects.all()
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@classmethod
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def filter(cls, *args, **kwargs):
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return cls.objects.filter(*args, **kwargs)
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@classmethod
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def get(cls, *args, **kwargs):
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return cls.objects.get(*args, **kwargs)
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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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DMLQuery(self.__class__, self, batch=self._batch).save()
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#reset the value managers
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for v in self._values.values():
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v.reset_previous_value()
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self._is_persisted = True
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return self
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def delete(self):
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""" Deletes this instance """
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DMLQuery(self.__class__, self, batch=self._batch).delete()
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@classmethod
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def _class_batch(cls, batch):
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return cls.objects.batch(batch)
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def _inst_batch(self, batch):
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self._batch = batch
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return self
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batch = hybrid_classmethod(_class_batch, _inst_batch)
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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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#get inherited properties
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inherited_columns = OrderedDict()
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for base in bases:
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for k,v in getattr(base, '_defined_columns', {}).items():
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inherited_columns.setdefault(k,v)
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#short circuit __abstract__ inheritance
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is_abstract = attrs['__abstract__'] = attrs.get('__abstract__', False)
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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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attrs[col_name] = ColumnDescriptor(col_obj)
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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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column_definitions = inherited_columns.items() + column_definitions
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defined_columns = OrderedDict(column_definitions)
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#prepend primary key if one hasn't been defined
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if not is_abstract and not any([v.primary_key for k,v in column_definitions]):
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raise ModelDefinitionException("At least 1 primary key is required.")
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counter_columns = [c for c in defined_columns.values() if isinstance(c, columns.Counter)]
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data_columns = [c for c in defined_columns.values() if not c.primary_key and not isinstance(c, columns.Counter)]
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if counter_columns and data_columns:
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raise ModelDefinitionException('counter models may not have data columns')
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has_partition_keys = any(v.partition_key for (k, v) in 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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# this will mark the first primary key column as a partition
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# key, if one hasn't been set already
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if not has_partition_keys and v.primary_key:
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v.partition_key = True
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has_partition_keys = True
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_transform_column(k,v)
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partition_keys = OrderedDict(k for k in primary_keys.items() if k[1].partition_key)
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clustering_keys = OrderedDict(k for k in primary_keys.items() if not k[1].partition_key)
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#setup partition key shortcut
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if len(partition_keys) == 0:
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if not is_abstract:
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raise ModelException("at least one partition key must be defined")
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if len(partition_keys) == 1:
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pk_name = partition_keys.keys()[0]
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attrs['pk'] = attrs[pk_name]
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else:
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# composite partition key case, get/set a tuple of values
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_get = lambda self: tuple(self._values[c].getval() for c in partition_keys.keys())
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_set = lambda self, val: tuple(self._values[c].setval(v) for (c, v) in zip(partition_keys.keys(), val))
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attrs['pk'] = property(_get, _set)
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# some validation
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col_names = set()
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for v in column_dict.values():
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# check for duplicate column names
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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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if v.clustering_order and not (v.primary_key and not v.partition_key):
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raise ModelException("clustering_order may be specified only for clustering primary keys")
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if v.clustering_order and v.clustering_order.lower() not in ('asc', 'desc'):
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raise ModelException("invalid clustering order {} for column {}".format(repr(v.clustering_order), v.db_field_name))
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col_names.add(v.db_field_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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#short circuit table_name inheritance
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attrs['table_name'] = attrs.get('__table_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['_defined_columns'] = defined_columns
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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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attrs['_partition_keys'] = partition_keys
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attrs['_clustering_keys'] = clustering_keys
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attrs['_has_counter'] = len(counter_columns) > 0
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#setup class exceptions
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DoesNotExistBase = None
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for base in bases:
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DoesNotExistBase = getattr(base, 'DoesNotExist', None)
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if DoesNotExistBase is not None: break
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DoesNotExistBase = DoesNotExistBase or attrs.pop('DoesNotExist', BaseModel.DoesNotExist)
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attrs['DoesNotExist'] = type('DoesNotExist', (DoesNotExistBase,), {})
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MultipleObjectsReturnedBase = None
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for base in bases:
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MultipleObjectsReturnedBase = getattr(base, 'MultipleObjectsReturned', None)
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if MultipleObjectsReturnedBase is not None: break
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MultipleObjectsReturnedBase = DoesNotExistBase or attrs.pop('MultipleObjectsReturned', BaseModel.MultipleObjectsReturned)
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attrs['MultipleObjectsReturned'] = type('MultipleObjectsReturned', (MultipleObjectsReturnedBase,), {})
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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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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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__abstract__ = True
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__metaclass__ = ModelMetaClass
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