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From mxmrlv <...@git.apache.org>
Subject [GitHub] incubator-ariatosca pull request #72: Aria 105 integrate modeling
Date Sun, 05 Mar 2017 14:17:28 GMT
Github user mxmrlv commented on a diff in the pull request:

    https://github.com/apache/incubator-ariatosca/pull/72#discussion_r104312850
  
    --- Diff: aria/modeling/bases.py ---
    @@ -0,0 +1,405 @@
    +# Licensed to the Apache Software Foundation (ASF) under one or more
    +# contributor license agreements.  See the NOTICE file distributed with
    +# this work for additional information regarding copyright ownership.
    +# The ASF licenses this file to You under the Apache License, Version 2.0
    +# (the "License"); you may not use this file except in compliance with
    +# the License.  You may obtain a copy of the License at
    +#
    +#     http://www.apache.org/licenses/LICENSE-2.0
    +#
    +# Unless required by applicable law or agreed to in writing, software
    +# distributed under the License is distributed on an "AS IS" BASIS,
    +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    +# See the License for the specific language governing permissions and
    +# limitations under the License.
    +
    +"""
    +ARIA's storage.structures module
    +Path: aria.storage.structures
    +
    +models module holds ARIA's models.
    +
    +classes:
    +    * ModelMixin - abstract model implementation.
    +    * ModelIDMixin - abstract model implementation with IDs.
    +"""
    +
    +from sqlalchemy.orm import relationship, backref
    +from sqlalchemy.orm.collections import attribute_mapped_collection
    +from sqlalchemy.ext import associationproxy
    +from sqlalchemy import (
    +    Column,
    +    ForeignKey,
    +    Integer,
    +    Text,
    +    Table,
    +)
    +
    +from . import utils
    +from ..utils import formatting
    +
    +
    +class ModelMixin(object):
    +
    +    @utils.classproperty
    +    def __modelname__(cls):                                                         
               # pylint: disable=no-self-argument
    +        return getattr(cls, '__mapiname__', cls.__tablename__)
    +
    +    @classmethod
    +    def id_column_name(cls):
    +        raise NotImplementedError
    +
    +    @classmethod
    +    def name_column_name(cls):
    +        raise NotImplementedError
    +
    +    @classmethod
    +    def foreign_key(cls, parent_table, nullable=False):
    +        """
    +        Return a ForeignKey object.
    +
    +        :param parent_table: Parent table name
    +        :param nullable: Should the column be allowed to remain empty
    +        """
    +        return Column(Integer,
    +                      ForeignKey('{table}.id'.format(table=parent_table),
    +                                 ondelete='CASCADE'),
    +                      nullable=nullable)
    +
    +    @classmethod
    +    def relationship_to_self(cls,
    +                             column_name,
    +                             relationship_kwargs=None):
    +        relationship_kwargs = relationship_kwargs or {}
    +
    +        remote_side = '{cls}.{remote_column}'.format(
    +            cls=cls.__name__,
    +            remote_column=cls.id_column_name()
    +        )
    +
    +        primaryjoin = '{remote_side} == {cls}.{column}'.format(
    +            remote_side=remote_side,
    +            cls=cls.__name__,
    +            column=column_name
    +        )
    +
    +        return relationship(
    +            cls._get_cls_by_tablename(cls.__tablename__).__name__,
    +            primaryjoin=primaryjoin,
    +            remote_side=remote_side,
    +            post_update=True,
    +            **relationship_kwargs
    +        )
    +
    +    @classmethod
    +    def one_to_many_relationship_to_self(cls,
    +                                         key,
    +                                         dict_key=None,
    +                                         relationship_kwargs=None):
    +        relationship_kwargs = relationship_kwargs or {}
    --- End diff --
    
    It has become somewhat problematic to figure out how the x_to_many relationships work,
since there must be a foreign key on the "many" side. This is exactly the issue we talked
about. it seems that using the `backref` could actually fix this. 


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