Question

我有一个包含1000个表的oracle db。我只想从20个表中读取。我使用过Automap extention＆amp;用于声明表类的元数据。

问题是有些表没有主键。

from config import E3_SQLALCHEMY_DATABASE_URI
from sqlalchemy import create_engine, MetaData, Column, String, Table
from sqlalchemy.orm import Session
from sqlalchemy.ext.automap import automap_base

engine = create_engine(E3_SQLALCHEMY_DATABASE_URI)
metadata = MetaData()
# auto-map db tables, list down the tables you want to query here
metadata.reflect(engine, only=['table_name1',
                               'table_name2',
                               'table_name3']}
Base = automap_base(metadata=metadata)
Base.prepare()
# db declaration
Table1 = Base.classes.table_name2
Table2 = Base.classes.table_name1
Table3 = Base.classes.table_name3
# create sqlalchemy session
session = Session(engine)

这导致Atrtibute错误，因为table3没有主键

我正在检查http://docs.sqlalchemy.org/en/rel_1_0/faq/ormconfiguration.html#how-do-i-map-a-table-that-has-no-primary-key，并试图在不直接更改db表的情况下添加主键。

我不知道该怎么做。我尝试过这几种方式。但都有错误。这是table3的模式，但是没有声明主键。

class Table3(Base):
    __table__ = 'table_name3'
    __table_args__ = {'extend_existing': True}
    # name = Column('name', String(1024), primary_key=True)
    # collection_key = Column('name', String(8192), primary_key=True)
    __mapper_args__ = {'primary_key': ['name', 'priority']}

我不想更改db表以添加primary_key，而是想在sqlalachemy中处理。因此，我尝试使用两个现有列，使用 mapper_args 声明主键。

In [40]: e3.query(FD_Group)
---------------------------------------------------------------------------
InvalidRequestError                       Traceback (most recent call last)
<ipython-input-40-6793c4942672> in <module>()
----> 1 e3.query(FD_Group)

C:\Python34\lib\site-packages\sqlalchemy\orm\session.py in query(self, *entities
, **kwargs)
   1247         :class:`.Session`."""
   1248
-> 1249         return self._query_cls(entities, self, **kwargs)
   1250
   1251     @property

C:\Python34\lib\site-packages\sqlalchemy\orm\query.py in __init__(self, entities
, session)
    108         self.session = session
    109         self._polymorphic_adapters = {}
--> 110         self._set_entities(entities)
    111
    112     def _set_entities(self, entities, entity_wrapper=None):

C:\Python34\lib\site-packages\sqlalchemy\orm\query.py in _set_entities(self, ent
ities, entity_wrapper)
    116         self._primary_entity = None
    117         for ent in util.to_list(entities):
--> 118             entity_wrapper(self, ent)
    119
    120         self._set_entity_selectables(self._entities)

C:\Python34\lib\site-packages\sqlalchemy\orm\query.py in __init__(self, query, c
olumn, namespace)
   3576             raise sa_exc.InvalidRequestError(
   3577                 "SQL expression, column, or mapped entity "
-> 3578                 "expected - got '%r'" % (column, )
   3579             )
   3580         elif not check_column:

InvalidRequestError: SQL expression, column, or mapped entity expected - got '<c
lass '__main__.FD_Group'>'

可以帮助如何在不添加数据库的情况下在Autobase中添加主列？

sqlalchemy automap添加主键

0 个答案: