Re: [sqlalchemy] Unexpected is_modified result after referencing a relationship
On Feb 27, 2015, at 4:48 PM, Eric Smith e...@esmithy.net wrote:
To those more experienced than me, does this behavior make sense? If so,
could you further my education with an explanation?
If I change an attribute, is_modified returns True (as expected).
If I then reference a relationship, is_modified returns False (unexpected).
My output for the following program (using SQLAlchemy 0.9.7) is:
False
True
False
Thanks,
Eric
from sqlalchemy import Column, Integer, String, create_engine, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
Base = declarative_base()
class Parent(Base):
__tablename__ = 'parent'
id = Column(Integer, primary_key=True, nullable=False)
message = Column(String)
children = relationship(Child, backref='parent')
class Child(Base):
__tablename__ = 'child'
id = Column(Integer, primary_key=True, nullable=False)
parent_id = Column(Integer, ForeignKey('parent.id'))
def main():
engine = create_engine('sqlite:///:memory:')
Session = sessionmaker(bind=engine)
Base.metadata.create_all(engine)
db = Session()
parent = Parent()
db.add(parent)
db.commit()
print db.is_modified(parent)
parent.message = hi
print db.is_modified(parent)
len(parent.children) # Should this change is_modified?
print db.is_modified(parent)
Turn on sql echoing, which is always the first step towards understanding ORM
behavior, and you'll see that the call to parent.children invokes a lazy load
operation, which is a Query hence it autoflushes first, thereby synchronizing
the state of message and resetting the modified flag.
if __name__ == '__main__':
main()
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Re: [sqlalchemy] relationship problem
On Feb 26, 2015, at 5:56 AM, Julien Cigar jci...@ulb.ac.be wrote: On Wed, Feb 25, 2015 at 06:10:55PM -0500, Michael Bayer wrote: Julien Cigar jci...@ulb.ac.be wrote: On Thu, Feb 19, 2015 at 11:31:10AM -0500, Michael Bayer wrote: Julien Cigar jci...@ulb.ac.be wrote: On Thu, Feb 19, 2015 at 02:45:43PM +0100, Julien Cigar wrote: Hello, I'm using SQLAlchemy 0.9.8 with PostgreSQL and the reflection feature of SQLAlchemy. I have the following tables (only relevant parts are show): https://gist.github.com/silenius/390bb9937490730741f2 and the problematic mapper is the one of my association object: https://gist.github.com/silenius/1559a7db65ed30a1b079 SQLAlchemy complains with the following error: sqlalchemy.exc.InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers. Original exception was: Could not locate any simple equality expressions involving locally mapped foreign key columns for primary join condition 'pool_invite_result.pool_invite_pool_id = pool_invite.pool_id AND pool_invite.pool_id = pool.id' on relationship PoolAccountResult.pool. Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or are annotated in the join condition with the foreign() annotation. To allow comparison operators other than '==', the relationship can be marked as viewonly=True. The problem is that in the PoolAccountResult mapper I want a relationship to the Pool but the link is made through an intermediate table (pool_invite) .. Any idea how to handle this with SQLAlchemy ? Thanks :) Julien ... and I'm answering to myself: it seems to work with https://gist.github.com/silenius/e7e59c96a7277fb5879f does it sound right ? Sure. Also, you could use automap which does figure these out in simple cases: http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/automap.html always with this, any idea why SQLAlchemy inserts NULL and NULL for my two relationship (line 51-79) instead of the pool_obj and dup.owner ids (line 89-90), https://dpaste.de/1Trz ..? getting a 404 on that link. Hi Mike, Thanks for your help! I took the time to make a complete test case, available from here https://gist.github.com/silenius/96d6ed2544d14753853f That's a very strange use of secondary, and I'm not sure I understand the rationale for an odd schema like this. It should be pretty clear that when a table is set up as secondary, it is only used as a linkage between those immediate classes and there are no features to track the state of this table otherwise as though it were a mapped class. Using the same secondary table in two unrelated relationships is not the intended use. Nevertheless, if you manipulate between Pool and User, that has no impact whatsoever on PoolInviteResult... Especially since we're dealing with a secondary table and not a first class mapped entity.You should add event listeners as needed on attributes such that when an in-Python change occurs between Pool and User, the desired change occurs for PoolInviteResult as well. I'm using PostgreSQL, and I checked that all constraints are properly created on server-side but I haven't checked with sqllite:// Thanks, Julien -- Julien Cigar Belgian Biodiversity Platform (http://www.biodiversity.be) PGP fingerprint: EEF9 F697 4B68 D275 7B11 6A25 B2BB 3710 A204 23C0 No trees were killed in the creation of this message. However, many electrons were terribly inconvenienced. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout. -- Julien Cigar Belgian Biodiversity Platform (http://www.biodiversity.be) PGP fingerprint: EEF9 F697 4B68 D275 7B11 6A25 B2BB 3710 A204 23C0 No trees were killed in the creation of this message. However, many electrons were terribly inconvenienced. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at
Re: [sqlalchemy] CheckConstraint in sqlalchemy-1.0.0dev
On Friday, 27 February 2015 09:52:36 UTC-6, Simon King wrote: On Fri, Feb 27, 2015 at 3:34 PM, Christopher Singley ch...@singleys.com javascript: wrote: I'm using the latest dev version of sqlalchemy against postgresql-9.4.1 I can't get SA to apply table-level CHECK constraints defined via declarative, although I can manually add them via psql to tables created by SA Metadata.create_all() Here's the code I'm testing with: https://gist.github.com/csingley/7783779320359dd5f74c Am I doing something wrong? I think you need to put your constraint into the __table_args__ attribute: http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/declarative/table_config.html Hope that helps, Simon Yep, that's what I was missing! Makes sense syntactically. Thank you sir. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] Unexpected is_modified result after referencing a relationship
To those more experienced than me, does this behavior make sense? If so,
could you further my education with an explanation?
If I change an attribute, is_modified returns True (as expected).
If I then reference a relationship, is_modified returns False (unexpected).
My output for the following program (using SQLAlchemy 0.9.7) is:
False
True
False
Thanks,
Eric
from sqlalchemy import Column, Integer, String, create_engine, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
Base = declarative_base()
class Parent(Base):
__tablename__ = 'parent'
id = Column(Integer, primary_key=True, nullable=False)
message = Column(String)
children = relationship(Child, backref='parent')
class Child(Base):
__tablename__ = 'child'
id = Column(Integer, primary_key=True, nullable=False)
parent_id = Column(Integer, ForeignKey('parent.id'))
def main():
engine = create_engine('sqlite:///:memory:')
Session = sessionmaker(bind=engine)
Base.metadata.create_all(engine)
db = Session()
parent = Parent()
db.add(parent)
db.commit()
print db.is_modified(parent)
parent.message = hi
print db.is_modified(parent)
len(parent.children) # Should this change is_modified?
print db.is_modified(parent)
if __name__ == '__main__':
main()
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