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I have an application which uses multiple databases. Once a model instance object is in memory, how can I determine what database it came from? Specifically I would like to know this for use in a method on the model class.
Example:
class book(Models.model):
newdate = models.DateField(default=date.today())
type = models.CharField(
max_length=30,
choices=BOOK_TYPE,
default = 'novel',
)
def get_current_student(self):
if not hasattr(self,'_current_student'):
try:
self._current_student = clickerlog.objects.using(SELF.ORIGIN_DATABASE).get(book=self.pk,end__isnull = True).student
except:
self._current_student = none
return self._current_student
class booklog(Models.model):
start = models.DateTimeField(
default=datetime.now(),
verbose_name = 'start time'
)
end = models.DateTimeField(null=True,blank=True,)
book = models.ForeignKey(book)
student = models.ForeignKey(student,
limit_choices_to = {'isactive':True})
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Django will complain if you try to assign or add an object of the wrong type. To retrieve objects from your database, construct a QuerySet via a Manager on your model class. A QuerySet represents a collection of objects from your database. It can have zero, one or many filters. Filters narrow down the query results based on the given parameters.
If you find yourself needing to write an SQL query that is too complex for Django’s database-mapper to handle, you can fall back on writing SQL by hand. Django has a couple of options for writing raw SQL queries; see Performing raw SQL queries. Finally, it’s important to note that the Django database layer is merely an interface to your database.
Once you’ve created your data models, Django automatically gives you a database-abstraction API that lets you create, retrieve, update and delete objects. This document explains how to use this API.
How to use get_object_or_404 () in a Django Project? This function calls the given model and get object from that if that object or model doesn’t exist it raise 404 error. Suppose we want to fetch 3rd product from the product model then we can use:
After a litte more digging I found it:
self._state.db
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