In looking at what you wrote doesn't this cause an fk violation (it does for me): 2018-10-08 10:18:38,760 INFO sqlalchemy.engine.base.Engine INSERT INTO employee (title_id, department_id, fund_id) VALUES (%(title_id)s, %(department_id)s, %(fund_id)s) RETURNING employee.id 2018-10-08 10:18:38,763 INFO sqlalchemy.engine.base.Engine INSERT INTO fund_title (title_id, department_id, fund_id) VALUES (%(title_id)s, %(department_id)s, %(fund_id)s) RETURNING fund_title.id
in that a a (non deferred) fk is violated between employee and fund_title ? On Mon, Oct 8, 2018 at 10:20 AM Mike Bayer <mike...@zzzcomputing.com> wrote: > On Sun, Oct 7, 2018 at 7:11 PM Alex Rothberg <agrothb...@gmail.com> wrote: > > > > Okay so I investigated / thought about this further. The issue is that > while I do have a relationship between the various models, some of the > relationships are viewonly since I have overlapping fks. > > > > For example I have a model Employee, which has fks: department_id, > title_id, and fund_id. The related models are Department (fk > department_id), Title (fk department_id and title_id) , Fund (fk fund_id) > and FundTitle (fk department_id, title_id and fund_id). I have set > FundTitle to viewonly. When updating / creating an Employee, I do create > and add a new FundTitle to the session, however I don't assign it to the > employee as the relationship is viewonly. If I don't flush before making > the assignment, the final flush / commit attempts to update / create the > employee before creating the FundTitle. > > let's work with source code that is runnable (e.g. MCVE). Below is > the model that it seems you are describing, and then there's a > demonstration of assembly of all those components using relationships, > a single flush and it all goes in in the correct order, all FKs are > nullable=False. > > from sqlalchemy import * > from sqlalchemy.orm import * > from sqlalchemy.ext.declarative import declarative_base > > Base = declarative_base() > > > class Employee(Base): > __tablename__ = 'employee' > id = Column(Integer, primary_key=True) > title_id = Column(ForeignKey('title.id'), nullable=False) > department_id = Column(ForeignKey('department.id'), nullable=False) > fund_id = Column(ForeignKey('fund.id'), nullable=False) > department = relationship("Department") > title = relationship("Title") > fund = relationship("Fund") > > > class Title(Base): > __tablename__ = 'title' > id = Column(Integer, primary_key=True) > department_id = Column(ForeignKey('department.id'), nullable=False) > department = relationship("Department") > > > class Department(Base): > __tablename__ = 'department' > id = Column(Integer, primary_key=True) > > > class Fund(Base): > __tablename__ = 'fund' > id = Column(Integer, primary_key=True) > title_id = Column(ForeignKey('title.id'), nullable=False) > department_id = Column(ForeignKey('department.id'), nullable=False) > department = relationship("Department") > title = relationship("Title") > > > class FundTitle(Base): > __tablename__ = 'fund_title' > id = Column(Integer, primary_key=True) > title_id = Column(ForeignKey('title.id'), nullable=False) > department_id = Column(ForeignKey('department.id'), nullable=False) > fund_id = Column(ForeignKey('fund.id'), nullable=False) > department = relationship("Department") > title = relationship("Title") > fund = relationship("Fund") > > e = create_engine("postgresql://scott:tiger@localhost/test", echo=True) > Base.metadata.create_all(e) > > s = Session(e) > > d1 = Department() > t1 = Title(department=d1) > f1 = Fund(department=d1, title=t1) > ft1 = FundTitle(title=t1, department=d1, fund=f1) > e1 = Employee(title=t1, department=d1, fund=f1) > > s.add_all([d1, t1, f1, ft1, e1]) > s.commit() > > > the INSERTs can be ordered naturally here and the unit of work will do > that for you if you use relationship: > > BEGIN (implicit) > 2018-10-08 10:18:38,750 INFO sqlalchemy.engine.base.Engine INSERT INTO > department DEFAULT VALUES RETURNING department.id > 2018-10-08 10:18:38,750 INFO sqlalchemy.engine.base.Engine {} > 2018-10-08 10:18:38,753 INFO sqlalchemy.engine.base.Engine INSERT INTO > title (department_id) VALUES (%(department_id)s) RETURNING title.id > 2018-10-08 10:18:38,753 INFO sqlalchemy.engine.base.Engine > {'department_id': 1} > 2018-10-08 10:18:38,757 INFO sqlalchemy.engine.base.Engine INSERT INTO > fund (title_id, department_id) VALUES (%(title_id)s, > %(department_id)s) RETURNING fund.id > 2018-10-08 10:18:38,757 INFO sqlalchemy.engine.base.Engine > {'title_id': 1, 'department_id': 1} > 2018-10-08 10:18:38,760 INFO sqlalchemy.engine.base.Engine INSERT INTO > employee (title_id, department_id, fund_id) VALUES (%(title_id)s, > %(department_id)s, %(fund_id)s) RETURNING employee.id > 2018-10-08 10:18:38,761 INFO sqlalchemy.engine.base.Engine > {'title_id': 1, 'department_id': 1, 'fund_id': 1} > 2018-10-08 10:18:38,763 INFO sqlalchemy.engine.base.Engine INSERT INTO > fund_title (title_id, department_id, fund_id) VALUES (%(title_id)s, > %(department_id)s, %(fund_id)s) RETURNING fund_title.id > 2018-10-08 10:18:38,764 INFO sqlalchemy.engine.base.Engine > {'title_id': 1, 'department_id': 1, 'fund_id': 1} > 2018-10-08 10:18:38,766 INFO sqlalchemy.engine.base.Engine COMMIT > > > > > > > > > On Tuesday, September 18, 2018 at 9:02:30 AM UTC-4, Mike Bayer wrote: > >> > >> if there are no dependencies between two particular objects of > >> different classes, say A and B, then there is no deterministic > >> ordering between them. For objects of the same class, they are > >> inserted in the order in which they were added to the Session. > >> > >> the correct way to solve this problem in SQLAlchemy is to use > >> relationship() fully. I know you've stated that these objects have a > >> relationship() between them but you have to actually use it, that is: > >> > >> obj_a = A() > >> obj_b = B() > >> > >> obj_a.some_relationship = obj_b # will definitely flush correctly > >> unless there is a bug > >> > >> OTOH if you are only using foreign key attributes, the ORM does *not* > >> have any idea in how it should be flushing these: > >> > >> obj_a = A() > >> obj_b = B() > >> > >> obj_a.some_fk = obj_b.some_id # ORM doesn't care about this, no > >> ordering is implied > >> > >> > >> since you said you're not setting any IDs, I'm not sure how you could > >> be doing the above. > >> > >> > >> > >> > >> > >> > >> On Tue, Sep 18, 2018 at 5:53 AM Simon King <si...@simonking.org.uk> > wrote: > >> > > >> > It's not something I've ever looked into, but I'm not aware of any > >> > debugging options here, no. You'd probably want to start by scattering > >> > print statements around the UOWTransaction class > >> > ( > https://bitbucket.org/zzzeek/sqlalchemy/src/c94d67892e68ac317d72eb202cca427084b3ca74/lib/sqlalchemy/orm/unitofwork.py?at=master&fileviewer=file-view-default#unitofwork.py-111 > ) > >> > > >> > Looking at that code made me wonder whether you've set any particular > >> > cascade options on your relationship; I'm not sure if cascade options > >> > affect the dependency calculation. > >> > > >> > Simon > >> > > >> > On Tue, Sep 18, 2018 at 5:28 AM Alex Rothberg <agrot...@gmail.com> > wrote: > >> > > > >> > > In order to guide me in stripping down this code to produce an > example for positing, are there any options / flags / introspections I can > turn on to understand how sql makes decisions about the order in which is > writes statements to the DB? > >> > > > >> > > On Friday, September 14, 2018 at 10:13:45 AM UTC-4, Simon King > wrote: > >> > >> > >> > >> In that case can you show us the code that is causing the problem? > >> > >> On Fri, Sep 14, 2018 at 2:55 PM Alex Rothberg <agrot...@gmail.com> > wrote: > >> > >> > > >> > >> > I am not generating any IDs myself and I already have > relationships between the models. > >> > >> > > >> > >> > On Friday, September 14, 2018 at 4:33:08 AM UTC-4, Simon King > wrote: > >> > >> >> > >> > >> >> On Thu, Sep 13, 2018 at 10:50 PM Alex Rothberg < > agrot...@gmail.com> wrote: > >> > >> >> > > >> > >> >> > Is it possible to hint at sqla the order in which it should > write out changes to the DB? > >> > >> >> > > >> > >> >> > I am having issues in which I add two new objects to a > session, a and b where a depends on b, but sqla is flushing a before b > leading to an fk issue. I can solve this a few ways: explicitly calling > flush after adding b, or changing the fk constraint to be initially > deferred. Ideally I would not have to do either of these. > >> > >> >> > > >> > >> >> > >> > >> >> If you have configured a relationship between the two classes > >> > >> >> ( > http://docs.sqlalchemy.org/en/latest/orm/tutorial.html#building-a-relationship > ), > >> > >> >> and you've linked the objects together using that relationship > (a.b = > >> > >> >> b), then SQLAlchemy will flush them in the correct order. If > you are > >> > >> >> generating your IDs in Python and assigning them to the primary > and > >> > >> >> foreign key columns directly, SQLAlchemy probably won't > understand the > >> > >> >> dependency. > >> > >> >> > >> > >> >> Does using a relationship fix your problem? > >> > >> >> > >> > >> >> Simon > >> > >> > > >> > >> > -- > >> > >> > SQLAlchemy - > >> > >> > The Python SQL Toolkit and Object Relational Mapper > >> > >> > > >> > >> > http://www.sqlalchemy.org/ > >> > >> > > >> > >> > To post example code, please provide an MCVE: Minimal, Complete, > and Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > >> > >> > --- > >> > >> > 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+...@googlegroups.com. > >> > >> > To post to this group, send email to sqlal...@googlegroups.com. > >> > >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> > >> > For more options, visit https://groups.google.com/d/optout. > >> > > > >> > > -- > >> > > SQLAlchemy - > >> > > The Python SQL Toolkit and Object Relational Mapper > >> > > > >> > > http://www.sqlalchemy.org/ > >> > > > >> > > To post example code, please provide an MCVE: Minimal, Complete, > and Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > >> > > --- > >> > > 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+...@googlegroups.com. > >> > > To post to this group, send email to sqlal...@googlegroups.com. > >> > > Visit this group at https://groups.google.com/group/sqlalchemy. > >> > > For more options, visit https://groups.google.com/d/optout. > >> > > >> > -- > >> > SQLAlchemy - > >> > The Python SQL Toolkit and Object Relational Mapper > >> > > >> > http://www.sqlalchemy.org/ > >> > > >> > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > >> > --- > >> > 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+...@googlegroups.com. > >> > To post to this group, send email to sqlal...@googlegroups.com. > >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> > For more options, visit https://groups.google.com/d/optout. > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > > --- > > 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 https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to a topic in the > Google Groups "sqlalchemy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sqlalchemy/fZMJQoI2qkY/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. 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