django-orm

问题 I am trying to find out the number of queries executed by a utility function. I have written a unit test for this function and the function is working well. What I would like to do is track the number of SQL queries executed by the function so that I can see if there is any improvement after some refactoring. def do_something_in_the_database(): # Does something in the database # return result class DoSomethingTests(django.test.TestCase): def test_function_returns_correct_values(self): self

问题 I am trying to find out the number of queries executed by a utility function. I have written a unit test for this function and the function is working well. What I would like to do is track the number of SQL queries executed by the function so that I can see if there is any improvement after some refactoring. def do_something_in_the_database(): # Does something in the database # return result class DoSomethingTests(django.test.TestCase): def test_function_returns_correct_values(self): self

问题 I'm trying to build two abstract classes called SurveyQuestionBase and SurveyResponseBase that will serve as templates to quickly define new concrete Models for implementing specific surveys on our website. The issue I am having is in enforcing that the SurveyResponseBase model, when made concrete, should define a ForeignKey to a concrete model of SurveyQuestionBase . Django does not allow us to define ForeignKeys to abstract classes so I cannot, for instance, do this: question = models

问题 I'm trying to build two abstract classes called SurveyQuestionBase and SurveyResponseBase that will serve as templates to quickly define new concrete Models for implementing specific surveys on our website. The issue I am having is in enforcing that the SurveyResponseBase model, when made concrete, should define a ForeignKey to a concrete model of SurveyQuestionBase . Django does not allow us to define ForeignKeys to abstract classes so I cannot, for instance, do this: question = models

问题 I want to copy images from one model to another within the project. Suppose these are my models: class BackgroundImage(models.Model): user = models.ForeignKey(User) image = models.ImageField(upload_to=get_upload_file_name) caption = models.CharField(max_length=200) pub_date = models.DateTimeField(default=datetime.now) class ProfilePicture(models.Model): user = models.ForeignKey(User) image = models.ImageField(upload_to=get_upload_file_name) caption = models.CharField(max_length=200) pub_date

问题 I want to copy images from one model to another within the project. Suppose these are my models: class BackgroundImage(models.Model): user = models.ForeignKey(User) image = models.ImageField(upload_to=get_upload_file_name) caption = models.CharField(max_length=200) pub_date = models.DateTimeField(default=datetime.now) class ProfilePicture(models.Model): user = models.ForeignKey(User) image = models.ImageField(upload_to=get_upload_file_name) caption = models.CharField(max_length=200) pub_date

问题 Similar to get_or_create, I would like to be able to update_or_create in Django. Until now, I have using an approaching similar to how @Daniel Roseman does it here. However, I'd like to do this more succinctly as a model method. This snippet is quite old and I was wondering if there is a better way to do this in more recent version of Django. 回答1: See QuerySet.update_or_create (new in Django 1.7dev) 回答2: There is update_or_create , eg:: obj, created = Person.objects.update_or_create( first

问题 I have a table like this Event table | id | status | date |order(FK)| | 1 | Planned | 05-02-2015 | 1 | | 2 | Delivered | 04-02-2015 | 2 | | 3 | Packed | 03-02-2015 | 3 | | 4 | Return | 06-02-2015 | 1 | I want output like this | id | status | date |order(FK)| | 2 | Delivered | 04-02-2015 | 2 | | 3 | Packed | 03-02-2015 | 3 | | 4 | Return | 06-02-2015 | 1 | I tried with query = Event.objects.annotate(order_num=Max('date')) but didn't got the expected result. How can i achieve this output 回答1:

问题 I used this SO question to enable full text search on a mysql db in Django application. # models.py class CaseSnapshot(BaseModel): text = models.TextField(blank=True) class Search(models.Lookup): lookup_name = "search" def as_mysql(self, compiler, connection): lhs, lhs_params = self.process_lhs(compiler, connection) rhs, rhs_params = self.process_rhs(compiler, connection) params = lhs_params + rhs_params return f"MATCH (%s) AGAINST (%s IN BOOLEAN MODE)" % (lhs, rhs), params models.TextField

问题 a = M.objects.filter(f__in=[None, 1]) a.query.__str__() u'SELECT * FROM "app_m" WHERE "app_m"."f" IN (None, 1)' dont you think that would be IN (NULL, 1) ? like: a = M.objects.filter(f=None) a.query.__str__() u'SELECT * FROM "app_m" WHERE "app_m"."f" IS NULL' Is this a default SQL behavior, django bug or I am missing something with f__in= ? thank you in advance! 回答1: a = M.objects.filter(Q(f__isnull=True) | Q(f__in=['1',...])) 回答2: It seems to be and old bug in Django (https://code