I'm getting an SAWarning (0.6.4 and also 0.7b5dev) which has a message
that confuses me, so I've duplicated the problem with a script:
===================================================
from sqlalchemy import *
from sqlalchemy.orm import *
engine = create_engine('sqlite:///', echo=True)
metadata = MetaData(engine)
session = sessionmaker(bind=engine)()
# association table
post_keywords = Table('post_keywords', metadata,
Column('post_id', Integer, ForeignKey('posts.id')),
Column('keyword_id', Integer, ForeignKey('keywords.id'))
)
posts_table = Table('posts', metadata,
Column('id', Integer, primary_key=True),
Column('headline', String(255), nullable=False),
Column('body', Text)
)
keywords_table = Table('keywords', metadata,
Column('id', Integer, primary_key=True),
Column('keyword', String(50), nullable=False, unique=True)
)
spotlights_table = Table('spotlights', metadata,
Column('id', Integer, primary_key=True),
Column('enddate', Date),
Column('post_id', Integer, ForeignKey('posts.id'))
)
class BlogPost(object):
def __init__(self, headline, body):
self.headline = headline
self.body = body
def __repr__(self):
return "BlogPost(%r, %r, %r)" % (self.headline, self.body,
self.author)
class Keyword(object):
def __init__(self, keyword):
self.keyword = keyword
class PostSpotLight(object):
pass
mapper(Keyword, keywords_table)
mapper(BlogPost, posts_table,
properties = {'keywords':
relationship(Keyword, secondary=post_keywords,
backref='posts')}
)
mapper(PostSpotLight, spotlights_table,
properties = {'postkeywords':
relationship(Keyword, secondary=post_keywords,
primaryjoin=spotlights_table.c.post_id==post_keywords.c.post_id)}
)
metadata.create_all(engine)
compile_mappers()
=========================================================
Here is the warning:
[...]/sqlalchemy-default/lib/sqlalchemy/orm/properties.py:900:
SAWarning: No ForeignKey objects were present in secondary table
'post_keywords'. Assumed referenced foreign key columns
'post_keywords.keyword_id', 'post_keywords.post_id' for join condition
'spotlights.post_id = post_keywords.post_id' on relationship
PostSpotLight.postkeywords
eq_pairs = self._sync_pairs_from_join(self.primaryjoin, True)
Why is the complaint that there are No ForeignKey objects were present
in secondary table 'post_keywords', when clearly there are?
***Furthermore, if I pass the relationship this:
foreign_keys=[post_keywords.c.post_id,post_keywords.c.keyword_id]
then the warning goes away, but all I've done is specify the very
foreign_keys that already exist.***
(I realize now I could also use an association proxy for the keywords
via the post, but the question remains.)
Thanks as always,
Kent
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