[sqlalchemy] Re: one to many relation, removing and adding list issue
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed instance
again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
hi,
The problem seems to be a little bit more general, I have a unique class (doing
nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map of
the session
Always the same session, I add again the python instance to the session, flush,
commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
from sqlalchemy import __version__, MetaData, Table, Column, Integer, String,
create_engine, orm #...@unresolvedimport
from sqlalchemy.orm import mapper #...@unresolvedimport
from sqlalchemy.orm import backref #...@unresolvedimport @UnusedImport
print __version__
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
class One(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return self.name
mapper_one = mapper(One,tb_one)
engine = create_engine('postgres://fma:fma6...@localhost:5432/postgres',
convert_unicode=True)
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
o1 = One(One)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.delete(o1)
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed instance
again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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[sqlalchemy] Re: one to many relation, removing and adding list issue
Sorry if you receive this twice, I am not sure if it had been
correctly posted.
On 26 août, 14:49, Martin-Leon Francois francois@gmail.com
wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
from sqlalchemy import __version__, MetaData, Table, Column, Integer, String,
create_engine, orm #...@unresolvedimport
from sqlalchemy.orm import mapper #...@unresolvedimport
from sqlalchemy.orm import backref #...@unresolvedimport @UnusedImport
print __version__
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
class One(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return self.name
mapper_one = mapper(One,tb_one)
engine = create_engine('postgres://fma:fma6...@localhost:5432/postgres',
convert_unicode=True)
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
o1 = One(One)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.delete(o1)
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
On Aug 26, 2010, at 8:49 AM, Martin-Leon Francois wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
OK this is a little strange. o1 has been deleted. You've found one
particular operation that doesn't immediately raise (add()), but anything else
you did with o1 would, for example:
print o1.name
you will get this (since o1 is expired and will refresh, then fail):
sqlalchemy.orm.exc.ObjectDeletedError: Instance 'One at 0x1288c70'
has been deleted.
as you've already figured out, o1 has state on it that tells SQLAlchemy that
this object is already persistent - no INSERT will be executed again for the
object. The strange part here is that the object is beyond persistent and is
in the deleted state, and we don't have an in-memory flag that would signal
this, though perhaps that is called for here, I've never seen anyone trying to
perform such an operation before.
Anyway to convert from persistent back to transient, use make_transient:
from sqlalchemy.orm import make_transient
make_transient(o1)
then the key is removed and the object is as though you just created it.
I want to check if there's some foolproof way we can block on add().
Also, the add()/add_all() calls are redundant as is the flush() right before
the commit().
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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You received this
Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
ok, many thx
fma
Le 26 août 2010 à 17:03, Michael Bayer a écrit :
On Aug 26, 2010, at 8:49 AM, Martin-Leon Francois wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of
the session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
OK this is a little strange. o1 has been deleted. You've found one
particular operation that doesn't immediately raise (add()), but anything
else you did with o1 would, for example:
print o1.name
you will get this (since o1 is expired and will refresh, then fail):
sqlalchemy.orm.exc.ObjectDeletedError: Instance 'One at 0x1288c70'
has been deleted.
as you've already figured out, o1 has state on it that tells SQLAlchemy that
this object is already persistent - no INSERT will be executed again for the
object. The strange part here is that the object is beyond persistent and
is in the deleted state, and we don't have an in-memory flag that would
signal this, though perhaps that is called for here, I've never seen anyone
trying to perform such an operation before.
Anyway to convert from persistent back to transient, use make_transient:
from sqlalchemy.orm import make_transient
make_transient(o1)
then the key is removed and the object is as though you just created it.
I want to check if there's some foolproof way we can block on add().
Also, the add()/add_all() calls are redundant as is the flush() right before
the commit().
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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