duplicate key value violates unique constraint itemstaticlabel_item_id_f9405967_uniq - django

Question

I know, this problem happens because the code is trying to add an entry to the database with a combination of unique keys that already exist. But my question is: why and how can I prevent this? It doesn't make sense to me that this is happening, given my logic.
I have this piece of code that basically stores some static label for an invoice. The idea is to create the label on the fly if it doesn't exist, instead of manually inserting it in a lot of places in the code.
Whenever an Item is generated, an ItemInv is also created, and by saving the latter, I check if a static label exists. If it doesn't, a new one is created. The code to get (or create) the static label is also called when displaying an Invoice / Draft.
The error seems to happen right there. The label doesn't exist, a new one is created, but somehow this happens twice? I mean, I really don't get why that code would try to add the same item two times. Could it be a thread issue?
I am not using get_or_create because some attributes on ItemStaticInv (static_account_label, static_agreement_label...) can be updated and not unique. Before creating the invoice, a draft has the same structure and the data can be changed, including these labels.
class ItemInv(managers.Model):
"""
Relation between Item and Invoice
"""
item = models.ForeignKey('Item')
invoice = models.ForeignKey('Invoice')
[...]
class Meta:
unique_together = ('item', 'invoice')
def save(self, *args, **kwargs):
iteminv = super(ItemInv, self).save(*args, **kwargs)
# If the item does not have the static information, one should be created
self.item.get_invoice_static(self.invoice)
return iteminv
class Item(managers.Model):
"""
Item to be put on an invoice
"""
serial = models.AutoField(primary_key=True) # Software license
product = models.ForeignKey('Product', verbose_name='Product')
account = models.ForeignKey('Account', verbose_name='Account', related_name='items')
[...]
def get_invoice_static(self, document):
try:
return self.document_labels.get(invoice=document)
except ObjectDoesNotExist:
return ItemStaticLabel.objects.create(
item=self,
invoice=document,
static_account_label=str(self.account),
static_customer_label=str(self.account.customer),
static_agreement_label=str(self.account.agreement)
)
class ItemStaticLabel(managers.Model):
"""
We must store static information about the Item on an invoice.
"""
item = models.ForeignKey('Item', related_name='document_labels')
invoice = models.ForeignKey('Invoice', related_name='item_labels')
static_account_label = models.CharField(max_length=256, null=True, blank=True)
static_customer_label = models.CharField(max_length=256, null=True, blank=True)
static_agreement_label = models.CharField(max_length=256, null=True, blank=True)
static_expiration_label = models.DateField(max_length=256, null=True, blank=True)
class Meta:
unique_together = ('item', 'invoice')
This has several flaws, but this system was developed by someone else and is on production. The amount of structural changes I can do are pretty much limited. Therefore I gotta try to understand what is causing this issue.
Traceback:
File "/home/apps/sites/invoice/source/v3/models.py" in get_invoice_static
1105. return self.document_labels.get(invoice=document)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
85. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/query.py" in get
380. self.model._meta.object_name
During handling of the above exception (ItemStaticLabel matching query does not exist.), another exception occurred:
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
65. return self.cursor.execute(sql, params)
The above exception (duplicate key value violates unique constraint "v3_itemstaticlabel_item_id_f9405967_uniq"
DETAIL: Key (item_id, invoice_id)=(1840, 1578) already exists.
) was the direct cause of the following exception:
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/core/handlers/exception.py" in inner
41. response = get_response(request)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/core/handlers/base.py" in _legacy_get_response
249. response = self._get_response(request)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/core/handlers/base.py" in _get_response
187. response = self.process_exception_by_middleware(e, request)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/core/handlers/base.py" in _get_response
185. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python3.4/contextlib.py" in inner
30. return func(*args, **kwds)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/views/generic/base.py" in view
68. return self.dispatch(request, *args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/views/generic/base.py" in dispatch
88. return handler(request, *args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/views/generic/detail.py" in get
116. context = self.get_context_data(object=self.object)
File "/home/apps/sites/invoice/source/web/views/invoice.py" in get_context_data
280. context['document_html'] = services.document_to_html(obj)
File "/home/apps/sites/invoice/source/v3/services.py" in document_to_html
1550. 'account': set_[0].get_invoice_static(document).static_account_label,
File "/home/apps/sites/invoice/source/v3/models.py" in get_invoice_static
1112. static_agreement_label=str(self.account.agreement)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
85. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/query.py" in create
394. obj.save(force_insert=True, using=self.db)
File "/home/apps/sites/invoice/source/v3/managers.py" in save
724. super().save(*args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/base.py" in save
808. force_update=force_update, update_fields=update_fields)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/base.py" in save_base
838. updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/base.py" in _save_table
924. result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/base.py" in _do_insert
963. using=using, raw=raw)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
85. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/query.py" in _insert
1076. return query.get_compiler(using=using).execute_sql(return_id)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/models/sql/compiler.py" in execute_sql
1107. cursor.execute(sql, params)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
65. return self.cursor.execute(sql, params)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/utils.py" in __exit__
94. six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/utils/six.py" in reraise
685. raise value.with_traceback(tb)
File "/home/apps/sites/invoice/env/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
65. return self.cursor.execute(sql, params)
Exception Type: IntegrityError at /invoice-menu/customer/251/invoices/1578/
Exception Value: duplicate key value violates unique constraint "v3_itemstaticlabel_item_id_f9405967_uniq"
DETAIL: Key (item_id, invoice_id)=(1840, 1578) already exists.
View
class InvoiceDetailView(DetailView):
model = Invoice
template_name = 'invoice_detail.html'
pk_url_kwarg = 'invoice_key'
context_object_name = 'invoice'
def get_context_data(self, **kwargs):
context = super(InvoiceDetailView, self).get_context_data(**kwargs)
obj = context[self.context_object_name]
obj = models.Invoice.objects.filter(pk=obj.pk).select_related(
'customer',
'customer__original',
'currency',
).prefetch_related(
'citems',
'citems__assocs',
'citems__assocs__product',
'iteminv_set',
'iteminv_set__item',
).first()
context['document_html'] = services.document_to_html(obj)
return context
Services
def document_to_html(document):
"""
Renders the invoice to html.
"""
from v3.models import Item, Maintenance, Invoice, CustomInvoiceLine
from web.collection_utils import collapse_list
data = {}
items = Item.objects.on_invoice(document)
mains = Maintenance.objects.on_invoice(document)
rows = get_invoice_product_rows(document)
# merge the lists
rows['itemrows'].extend(rows['mainrows'])
include_summary = len(rows['itemrows']) > 0 and not Invoice.objects.filter(creditted_by=document)
# calc VAT lines
vats = {}
for ir in rows['itemrows']:
row = ir['line']
vat = ir['objs'][0].vat
rate = ir['objs'][0].vat_rate
total = (Decimal(rate / 100) * ir['rowtotal']).quantize(Decimal('.01'), rounding=ROUND_HALF_UP)
try:
vats[vat]['rownums'].append(row)
vats[vat]['total'] += total
except:
vats[vat] = dict(rownums=[row, ], message=ir['objs'][0].vat_message, total=total, rate=rate)
for mr in rows['mainrows']:
row = mr['line']
vat = mr['objs'][0].vat
rate = mr['objs'][0].vat_rate
total = (Decimal(rate / 100) * mr['rowtotal']).quantize(Decimal('.01'), rounding=ROUND_HALF_UP)
try:
vats[vat]['rownums'].append(row)
# Changed it to not add any value because that will produce wrong vat output.
vats[vat]['total'] += 0
except:
vats[vat] = dict(rownums=[row, ], message=mr['objs'][0].vat_message, total=total, rate=rate)
for cr in rows['citemrows']:
row = cr['line']
vat = cr['obj'].vat
rate = cr['obj'].vat_rate
total = (Decimal(rate / 100) * cr['rowtotal']).quantize(Decimal('.01'), rounding=ROUND_HALF_UP)
try:
vats[vat]['rownums'].append(row)
vats[vat]['total'] += total
except:
vats[vat] = [row, ]
vats[vat] = dict(rownums=[row, ], message=cr['obj'].vat_message, total=total, rate=rate)
vats = [(k, collapse_list(v['rownums']), v['message'], v['total'], v['rate']) for (k, v) in vats.items()]
vats = sorted(vats, key=lambda x: x[1])
# Gather data for the license agreement overview
# A list of lists, where the inner lists contain items that match on product and account
matched_item_sets = []
items = list(items) + list([m.serial for m in mains])
for item in items:
# Find a set to add this item to
for set_ in matched_item_sets:
if item.product == set_[0].product and item.account == set_[0].account:
if item not in set_:
set_.append(item)
break
else:
# No matching set found. Create a new one
matched_item_sets.append([item])
# Package the item sets nicely with meta information
summary = []
for set_ in matched_item_sets:
summary.append({
'account': set_[0].get_invoice_static(document).static_account_label,
'owner': set_[0].get_invoice_static(document).static_customer_label,
'agreement': set_[0].get_invoice_static(document).static_agreement_label,
'product': set_[0].product,
'licenses': collapse_list(set_),
})
data['inv'] = document
data['lines'] = rows['itemrows']
data['citems'] = rows['citemrows']
data['vats'] = vats
data['lagree'] = summary
data['includeSummary'] = include_summary
data['cilines'] = CustomInvoiceLine.objects.filter(invoice=document, on_invoice=True)
data['base_url'] = settings.SITE_BASE_URL
tpl = document.template
tpl = DjangoTemplate(tpl.content)
return tpl.render(Context(data))