Hello Michael
Sorry for the late reply.
So, below is my full stack trace:
Traceback (most recent call last):
File
/Users/foobar/Developpement/nursery_project/applications/nurserydb/utils_scripts/test2.py,
line 64, in module
plant.taxon = taxon_new # triggers an IntegrityError
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 303, in __set__
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 804, in set
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 824, in fire_replace_event
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 1131, in emit_backref_from_scalar_set_event
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 638, in append
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 788, in set
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/attributes.py,
line 613, in get
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/strategies.py,
line 524, in _load_for_state
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/strategies.py,
line 585, in _emit_lazyload
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/query.py, line
2104, in all
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/query.py, line
2215, in __iter__
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/session.py, line
1138, in _autoflush
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/session.py, line
1817, in flush
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/session.py, line
1935, in _flush
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/util/langhelpers.py,
line 58, in __exit__
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/session.py, line
1899, in _flush
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/unitofwork.py,
line 372, in execute
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/unitofwork.py,
line 525, in execute
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/persistence.py,
line 58, in save_obj
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/orm/persistence.py,
line 491, in _emit_update_statements
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/base.py, line
662, in execute
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/base.py, line
761, in _execute_clauseelement
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/base.py, line
874, in _execute_context
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/base.py, line
1024, in _handle_dbapi_exception
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/util/compat.py, line
163, in raise_from_cause
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/base.py, line
867, in _execute_context
File build/bdist.macosx-10.6-x86_64/egg/sqlalchemy/engine/default.py,
line 324, in do_execute
sqlalchemy.exc.IntegrityError: (IntegrityError) null value in column
taxon_id violates not-null constraint
'UPDATE botany.plant SET taxon_id=%(taxon_id)s WHERE botany.plant.id =
%(botany_plant_id)s' {'taxon_id': None, 'botany_plant_id': -2147483643}
I guess it correspond to what you mentioned.
I have tried to use what you told :
with session.no_autoflush:
plant.taxon = taxon_new
...and it works fine.
But the thing is that I don't need it in case I comment out the line :
taxon_old = session.query(Taxon).get(-2147483634)
and the test:
print plant.taxon is taxon_old # True
It seems that the problems occurs because the taxon_old is already loaded
in the identity map so the taxon.plant of the already loaded taxon_old must
be changed to reflect the change made by the below line:
plant.taxon = taxon_new # triggers an IntegrityError
This is totally understandable.
However, I get confused by SQLAlchemy trying to set taxon_id to NULL or
even worse, by SQLAlchemy trying to delete the plant if I configure a
cascade='all, delete-orphan' on the backref side of the relationship. I
understand that it might not be easy for SQLAlchemy to understand what I
am trying to do, but the fact that I end up with two different results
depending on whether or not taxon_old is previously loaded is confusing.
Anyway, SQLAlchemy is still very impressive and never ceases to amaze me
every day I discover new features. Thank you for that.
Le mardi 4 juin 2013 16:38:30 UTC+2, Etienne Rouxel a écrit :
Hello
I would like to change a value in a one-to-one relationship but I cannot
because of some actions that SQLAlchemy try to do, and I don't know why.
Here is my simplified code :
# -*- coding: utf-8 -*-
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
_taxon_table = Table('taxon', Base.metadata,
Column('id', Integer, primary_key=True),
schema='botany'
)
_foliagetype_table = Table('foliagetype', Base.metadata,
