Hello,
I'm experiencing what looks like a bug in SQLAlchemy 0.9.1 through 0.9.8. I
use Python 2.7.6. This is the situation:
I have an SQLite database with a many-to-many relationship. This
relationship is created using a secondary table, with a left and a right
foreign key column. I make use of sqlalchemy.ext.automap to load the table
classes for an existing database:
engine = sqlalchemy.create_engine('sqlite:///{0}'.format(DB_PATH), echo=
True)
Session = sessionmaker(bind=engine)
session = Session()
metadata = sqlalchemy.MetaData()
metadata.reflect(bind=engine)
Base = automap_base(metadata=metadata)
Base.prepare()
Photo = Base.classes.photos
Taxon = Base.classes.taxa
Rank = Base.classes.ranks
Because of the many-to-many relationship between Photo and Taxon, I can
access the Photo.taxa_collection attribute to get the related taxa for a
photo. The problem is that in some cases the collection attributes are not
created. For example, if I set the echo attribute for
sqlalchemy.create_engine() to False or True (differs per SQLAlchemy
version), the script will crash with this error:
Traceback (most recent call last):
File "./sqla_bug_test_a.py", line 149, in <module>
main()
File "./sqla_bug_test_a.py", line 126, in main
q = get_photos_with_taxa(session, metadata)
File "./sqla_bug_test_a.py", line 140, in get_photos_with_taxa
join(Photo.taxa_collection).join(Taxon.ranks).\
AttributeError: type object 'photos' has no attribute 'taxa_collection'
The collection attributes are not created in this case. The same sometimes
happens when I import certain Python modules (e.g. logging or argparse) before
sqlalchemy is imported. Sometimes it has to be a combination of these two.
I have created a Python script that demonstrates the problem:
https://gist.github.com/figure002/2d98ce8532668f9f1bc1
In the comment section below I've included download links to test SQLite
databases. In the script I also included some test results for different
versions of SQLAlchemy, though the results aren't always consistent.
Is this indeed a bug and should I file a bug report? Is there a workaround for
this problem?
Regards,
Serrano
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