Hi all,
I'm having some trouble defining cyclical FK references in my models.
I understand from the documentation that specifying post_update=True
on the relation definition should effectively remove that edge from
the dependency graph.
However, the following code still gives CircularDependencyErrors
(stack trace at the end) -- this is SA 0.4.2p3:
tableA = Table('tableA', metadata,
Column('a_id', Integer, primary_key=True),
Column('b_id', Integer, ForeignKey('tableB.b_id',
onupdate="CASCADE", ondelete="CASCADE")),
mysql_engine='InnoDB'
)
tableB = Table('tableB', metadata,
Column('b_id', Integer, primary_key=True),
Column('a_id', Integer, ForeignKey('tableA.a_id',
onupdate='CASCADE', ondelete='CASCADE')),
mysql_engine="InnoDB"
)
class A(object):
pass
class B(object):
pass
mapper(A, tableA,
properties=dict(
b = relation(B)
)
)
mapper(B, tableB,
properties = dict(
a = relation(A, post_update=True)
)
)
Any suggestions on how to tackle this?
Thanks a lot!
James
------------ Stack Trace -------------
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/Current/bin/tg-
admin", line 8, in <module>
load_entry_point('TurboGears==1.0.4.2', 'console_scripts', 'tg-
admin')()
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/TurboGears-1.0.4.2-py2.5.egg/turbogears/
command/base.py", line 371, in main
command.run()
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/TurboGears-1.0.4.2-py2.5.egg/turbogears/
command/base.py", line 97, in run
sacommand(command, sys.argv)
File "<string>", line 5, in sacommand
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/TurboGears-1.0.4.2-py2.5.egg/turbogears/
command/sacommand.py", line 33, in create
metadata.create_all()
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/
schema.py", line 1215, in create_all
bind.create(self, checkfirst=checkfirst, tables=tables)
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/engine/
base.py", line 1131, in create
self._run_visitor(self.dialect.schemagenerator, entity,
connection=connection, **kwargs)
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/engine/
base.py", line 1160, in _run_visitor
visitorcallable(self.dialect, conn, **kwargs).traverse(element)
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/sql/
visitors.py", line 76, in traverse
meth(target)
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/sql/
compiler.py", line 758, in visit_metadata
collection = [t for t in metadata.table_iterator(reverse=False,
tables=self.tables) if (not self.checkfirst or not
self.dialect.has_table(self.connection, t.name, schema=t.schema))]
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/
schema.py", line 1133, in table_iterator
return iter(sort_tables(tables, reverse=reverse))
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/sql/
util.py", line 19, in sort_tables
sequence = topological.sort(tuples, tables)
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/
topological.py", line 32, in sort
return [n.item for n in _sort(tuples, allitems,
allow_cycles=False, ignore_self_cycles=True)]
File "/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/site-packages/SQLAlchemy-0.4.2p3-py2.5.egg/sqlalchemy/
topological.py", line 216, in _sort
raise CircularDependencyError("Circular dependency detected " +
repr(edges) + repr(queue))
sqlalchemy.exceptions.CircularDependencyError: Circular dependency
detected [(tableA, tableB), (tableB, tableA)][]
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