ah ill take a look, it is definitely sensitive to recursion issues
which I thought i had fixed but I will try that one out. the remove
() issue is probably just a method that I am not covering properly.
I also might want to look more closely at the case where, you loaded
object A, object B has the list still triggered to be lazy-
loaded...then deleting from A, does that trigger the lazy load on B
before trying to remove the item ? its a pretty intricate situation.
It might be enlightening if you tried out some of your test cases
within the AttributesTest.testbackref test in the attributes.py test
suite. This test suite is not using any mappers or database access,
just strictly the "attributes" package which supplies the property
decorators on classes, and the many-to-many test deals with pretty
much one object called a ListBackrefExtension, that talks to two
HistoryList objects. its a pretty focused test on just this whole
"circular relationship" idea.
On Dec 14, 2005, at 7:47 PM, Robert Leftwich wrote:
Michael Bayer wrote:
hey folks -
I just checked in the "backref" feature.
There is a recursion problem when deleting items out of a m:n
mapped relationship:
studentTbl = Table('student', engine, Column
('name', String, primary_key=True))
courseTbl = Table('course', engine, Column
('name', String, primary_key=True))
enrolTbl = Table('enrol', engine,
Column('student_id',
String, ForeignKey
('student.name'), primary_key=True),
Column('course_id',
String, ForeignKey
('course.name'), primary_key=True))
class Student(object):
def __init__(self, name=''):
self.name = name
class Course(object):
def __init__(self, name=''):
self.name = name
Student.mapper = mapper(Student, studentTbl)
Course.mapper = mapper(Course, courseTbl, properties =
{'students': relation(Student.mapper, enrolTbl, lazy=True,
backref='courses')})
studentTbl.create()
courseTbl.create()
enrolTbl.create()
s1 = Student('Student1')
c1 = Course('Course1')
c2 = Course('Course2')
c3 = Course('Course3')
s1.courses.append(c1)
s1.courses.append(c2)
c1.students.append(s1)
c3.students.append(s1)
assert len(s1.courses) == 3
assert len(c1.students) == 1
objectstore.commit()
objectstore.clear()
s = Student.mapper.get_by(name='Student1')
c = Course.mapper.get_by(name='Course3')
assert len(s.courses) == 3
del s.courses[1]
assert len(s.courses) == 2
... RuntimeError: maximum recursion depth exceeded...
Also, there are some instances when I delete an item that I'm
getting the following error:
IndexError: list assignment index out of range
Traceback:
....
File "/home/robert/tools/python/sqlalchemy/lib/sqlalchemy/
util.py", line 259, in __delitem__
del self.data[i]
but I haven't been able to distil it down to a small test case as
yet - it always triggers the recursion problem.
Lastly, if I use remove() instead of del in the first test, i.e.
assert len(s.courses) == 3
s.courses.remove(c2)
assert len(s.courses) == 2
There is no recursion error, but the last assertion fails, i.e. the
remove() hasn't actually removed c2.
Hopefully, these problems are all related (excuse the pun:-))
Robert
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