Django - How to do a transaction when saving a form? - django

Question

I'm saving a form, but there is one save() method that is outside the transaction. The save() method outside a transaction is the save() on the "BicycleAdCategoryForm".
Here is the code:
models.py
class Main(models.Model):
section = models.ForeignKey(Section)
user = models.ForeignKey(User)
title = models.CharField(max_length=250)
date_inserted = models.DateTimeField(auto_now_add=True)
date_last_update = models.DateTimeField(auto_now=True)
def __unicode__(self):
return self.title
# To order in the admin by name of the section
class Meta:
ordering = ['date_inserted']
class BicycleAd(models.Model):
main = models.ForeignKey(Main)
bicycleadtype = models.ForeignKey(BicycleAdType)
bicycleaditemkind = models.ForeignKey(BicycleAdItemKind) # MPTT Model
bicycleadcondition = models.ForeignKey(BicycleAdCondition)
country = models.ForeignKey(GeonamesCountry)
city = models.ForeignKey(GeonamesLocal)
date_inserted = models.DateTimeField(auto_now_add=True)
date_last_update = models.DateTimeField(auto_now=True)
# To order in the admin by name of the section
class Meta:
ordering = ['date_inserted']
class BicycleAdCategoryType(models.Model):
n_bicycle_ad_category_type = models.CharField(max_length=100) # COMPRA, VENDA, TROCA
date_inserted = models.DateTimeField(auto_now_add=True)
date_last_update = models.DateTimeField(auto_now=True)
def __unicode__(self):
return self.n_bicycle_ad_category_type
# To order in the admin by name of the section
class Meta:
ordering = ['n_bicycle_ad_category_type']
forms.py
class MainForm(forms.ModelForm):
class Meta:
model = Main
exclude = ('user', 'section')
class BicycleAdForm(forms.ModelForm):
class Meta:
model = BicycleAd
exclude = ('main', 'bicycleadtype', 'bicycleaditemkind', 'bicycleadcondition', 'city') # DPS RETIRAR DAQUI A "CITY"
class BicycleAdCategoryForm(forms.ModelForm):
bicycleadcategorytype = forms.ModelMultipleChoiceField(queryset=BicycleAdCategoryType.objects.all(), required=False, widget=forms.CheckboxSelectMultiple) # Se retirar o widget fico uma SELECT box em q posso selecionar varias opcoes
class Meta:
model = BicycleAdCategory
exclude = ('bicyclead',)
def save(self, commit, rel_obj):
data = self.data.getlist('bicycleadcategorytype')
for item in data:
obj_bicycleadcategory = BicycleAdCategory()
obj_bicycleadcategory.bicyclead = rel_obj
obj_bicycleadcategory.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=item)
obj_bicycleadcategory.save()
def clean_bicycleadcategorytype(self):
data = self.cleaned_data['bicycleadcategorytype']
try:
for item in data:
bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=item.pk)
return bicycleadcategorytype
except (KeyError, BicycleAdCategoryType.DoesNotExist):
raise forms.ValidationError('Invalid Bicycle Ad Category Type. Please try again.')
views.py
def submit_ad_view(request):
if request.method == 'POST':
model_main = Main()
model_main.section = Section.objects.get(pk=request.POST['section'])
model_main.user = request.user
model_bicyclead = BicycleAd()
model_bicyclead.bicycleadtype = BicycleAdType.objects.get(pk=2)
model_bicyclead.bicycleaditemkind = BicycleAdItemKind.objects.get(pk=4)
model_bicyclead.bicycleadcondition = BicycleAdCondition.objects.get(pk=2)
model_bicyclead.city = GeonamesLocal.objects.get(pk=4803854)
form_main = MainForm(request.POST, instance = model_main)
form_bicyclead = BicycleAdForm(request.POST, instance = model_bicyclead)
form_bicycleadcategory = BicycleAdCategoryForm(request.POST)
if form_main.is_valid() and form_bicyclead.is_valid() and form_bicycleadcategory.is_valid():
main_f = form_main.save()
bicyclead_f = form_bicyclead.save(commit=False)
bicyclead_f.main = main_f
bicyclead_f.save()
bicycleadcategory_f = form_bicycleadcategory.save(commit=False, rel_obj=model_bicyclead)
resultado = 'valid'
else:
resultado = 'n_valid'
return render_to_response('app/submit_ad.html', {'resultado': resultado}, context_instance=RequestContext(request))
I think main_f and bicyclead_f are inside a transaction but bicycleadcategory_f is outside a transaction. When bicycleadcategory_f fails, main_f and bicyclead_f are stored in the database.
Any clue on what I'm doing wrong?
Best Regards,

Answer 1

Django executes views using the commit_on_success decorator (or at least it behaves that way). If you're view crashes (uncaught exceptions), a rollback should take place. If some data is stored, and some is not there is a possibility that your DB engine does not support transactional processing.
Check out the django doc for more info
https://docs.djangoproject.com/en/dev/ref/databases/
For example, if you're using MySQL with MyISAM you may encounter some problems
edit:
Krzysiek Szularz: I guess everybody is using django TransactionMiddleware or simmilar things, so I skipped it - and mentioned only the logic layer.