我想将旧的sqlite3代码转换为SQL炼金术。我试图理解如何最好地处理我的用例。我是数据库访问的ORM方法的新手。动态表名与SQLalchemy
我想动态生成基于通用定义的唯一表名。我已阅读mixins guide以及如何使用type
to dynamically declare classes的帖子,但我仍然不确定如何去做这件事。以下是我迄今为止:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Table, Column, Integer, String, MetaData, ForeignKey
from sqlalchemy.ext.declarative import declared_attr
Base = declarative_base()
class DynamicName(object):
@declared_attr
def __tablename__(cls):
return cls.__name__.lower()
class Genome(DynamicName, Base):
__tablename__ = 'AbstractGenome'
AlignmentId = Column(Integer, primary_key=True)
StartOutOfFrame = Column(Integer)
BadFrame = Column(Integer)
def build_genome_table(genome):
d = {'__tablename__': genome}
table = type(genome, (Genome,), d)
return table
如果我尝试使用这个,这是行不通的:
>>> from sqlalchemy import create_engine
>>> engine = create_engine('sqlite:///:memory:', echo=True)
>>> genomes = ["A", "B"]
>>> tables = {x: build_genome_table(x) for x in genomes}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 1, in <dictcomp>
File "<stdin>", line 3, in build_genome_table
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/api.py", line 55, in __init__
_as_declarative(cls, classname, cls.__dict__)
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 88, in _as_declarative
_MapperConfig.setup_mapping(cls, classname, dict_)
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 103, in setup_mapping
cfg_cls(cls_, classname, dict_)
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 135, in __init__
self._early_mapping()
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 138, in _early_mapping
self.map()
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 529, in map
**self.mapper_args
File "<string>", line 2, in mapper
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 623, in __init__
self._configure_inheritance()
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 930, in _configure_inheritance
self.local_table)
File "<string>", line 2, in join_condition
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/sqlalchemy/sql/selectable.py", line 839, in _join_condition
(a.description, b.description, hint))
sqlalchemy.exc.NoForeignKeysError: Can't find any foreign key relationships between 'AbstractGenome' and 'A'.
我如何去根据传递的名称有关动态生成Genome
表?我最好也喜欢一个可以有层次继承的设置,以便我可以声明不同的子类,如ReferenceGenome
或TargetGenome
,它们具有附加列,但也可以具有动态名称。
SQLAlchemy试图设置继承和失败,因为'A'表和'AbstractGenome'表之间没有外键。你真的打算创建'A'表和'AbstractGenome'表吗?如果没有,你应该在''Genome'定义中加入'__abstract__ = True'。 – univerio