Hi everyone,
I have items that have an order. This function is supposed to move items
up (swapping the order with the previous item) or down (...). I tried
doing it via a transaction (as 'order' is logically unique), but on the
first save() it fails with a ProgrammingError:
@transaction.commit_manually
def move_item_with_order(item, direction):
second_item = None
if direction == 'up':
# are there items with a lower order?
qs = item.__class__.objects.all().filter(order__lt=item.order)
if qs.count() > 0:
second_item = qs.order_by("-order")[0]
elif direction == 'down':
# are there items with a higher order?
qs = item.__class__.objects.all().filter(order__gt=item.order)
if qs.count() > 0:
second_item = qs.order_by("order")[0]
if second_item:
item.order, second_item.order = second_item.order, item.order
item.save()
second_item.save()
transaction.commit()
this seems like a textbook example of something where you need to start
a transaction, and I'm not understanding what I do wrong...
Any clues?
- bram
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