On 4 Jul., 17:05, Michael Bayer <mike...@zzzcomputing.com> wrote:
> remove the item using remove(). What's the "items must be in a list
> rule", the not nullable foreign key ? thats what "delete-orphan"
> cascade is for, its in the tutorial and reference documentation.
Thanks, this works for the simple case in my first example. However,
consider inserting the item in two ordered lists. If you remove it by
the list method in one list, the position information is properly
updated for *this* list. But not for the other list. See the following
example:
------------------------
# -*- encoding: utf-8 -*-
from sqlalchemy import create_engine, MetaData, Table, Column,
Integer, Unicode, ForeignKey, UniqueConstraint
from sqlalchemy.orm import sessionmaker, mapper, relation
from sqlalchemy.ext.orderinglist import ordering_list
metadata = MetaData()
stock_table = Table("stock", metadata,
Column("id", Integer, primary_key=True),
Column("name", Unicode, unique=True))
list_table = Table("list", metadata,
Column("id", Integer, primary_key=True),
Column("name", Unicode, unique=True))
item_table = Table("item", metadata,
Column("id", Integer, primary_key=True),
Column("name", Unicode, unique=True),
Column("stockpos", Integer),
Column("stock_id", Integer, ForeignKey("stock.id"),
nullable=False),
Column("listpos", Integer),
Column("list_id", Integer, ForeignKey("list.id"),
nullable=False),
UniqueConstraint("stock_id", "name"),
UniqueConstraint("list_id", "name"))
class Stock(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return "<Stock %s>" % self.name
class List(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return "<List %s>" % self.name
class Item(object):
def __init__(self, name, stock, list):
self.name = name
self.stock = stock
self.list = list
def __repr__(self):
return "<Item %s part of %s at position %s and %s at position
%s>" % (self.name, self.stock, self.stockpos, self.list, self.listpos)
mapper(Stock, stock_table,
properties={"items": relation(Item,
backref="stock",
order_by=[item_table.c.stockpos],
collection_class=ordering_list
("stockpos"),
cascade="save-
update,merge,delete,delete-orphan")})
mapper(List, list_table,
properties={"items": relation(Item,
backref="list",
order_by=[item_table.c.listpos],
collection_class=ordering_list
("listpos"),
cascade="save-
update,merge,delete,delete-orphan")})
mapper(Item, item_table)
engine = create_engine("postgres:///list", echo=True)
metadata.bind = engine
stock_table.create()
list_table.create()
item_table.create()
Session = sessionmaker(engine)
session = Session()
s = Stock(u"items")
l1 = List(u"a")
l2 = List(u"b")
i1 = Item(u"i1", s, l1)
i2 = Item(u"i2", s, l1)
i3 = Item(u"i3", s, l2)
i4 = Item(u"i4", s, l2)
session.add(s)
session.commit()
# up to this point everything is fine
s.items.remove(i3)
session.commit()
print i4 # listpos should be 0, but it is 1 (i.e. not updated)
session.close()
engine.dispose()
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