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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