On Oct 24, 2008, at 9:08 PM, jack2318 wrote:
>
> I am really sorry but I pressed POST before I was ready. So again the
> code (without comments)
>
>
> session = Session()
> order = session.query(dbOutOrder).get(2)
>
> for line in order.lines:
> session.delete(line)
> session.flush()
>
> for i in range(1,10):
> line = dbOutLine()
> line.HEADER_id = order.id
> line.ITEM_SKU_id = 1
> line.QTY = 1
>
> order.lines.append(line)
>
> session.add(order)
> session.flush()
>
> i = 0
> for line in order.lines:
> if i % 2 == 0:
> print "DELETE"
> session.delete(line)
> i += 1
> session.commit()
>
>
> and the mappers:
> mOutOrder = mapper(dbOutOrder, tbl_outHeader, properties={'lines':
> relation(dbOutLine)})
> mOutLine = mapper(dbOutLine, tbl_outLine)
>
> as soon as I get to commit I get error:
>
> Unexpected error: <class
> 'sqlalchemy.orm.exc.ConcurrentModificationError'> Deleted rowcount 5
> does not match number of objects deleted 7
>
> What I am doing wrong? Of course if I issue commit after first delete
> everything is fine.
session.delete(someobject) does not remove the object from
collections. You're issuing delete() on some of the members of
order.lines twice (delete() puts them back into the session after
they've been removed). If you issue a commit(), the order.lines
collection is expired so it refreshes the most current data on next
access and therefore the problem is eliminated.
Instead of issuing delete() on collection members, just remove them
from the collection and use cascade="all, delete-orphan" on the
order.lines relation.
also "order" is already in the session; no need to add() it a second
time.
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