Question

I need to filter database by default every time that I see it (when I save changes or when I open database first time).
Can anybody tell me how to do it?

Answer 1

This is possible with custom custom Managers:

Say you have a class called Book:

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=50)

And you want the admin pages for book objects to only show books by Roald Dahl, then you can add a custom manager:

class DahlBookManager(models.Manager):
    def get_query_set(self):
        return super(DahlBookManager, self).get_query_set().filter(author='Roald Dahl')

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=50)

    objects = models.Manager()
    dahl_objects = DahlBookManager()

Then you just need to specify that your ModelAdmin should use the dahl_objects manager, which is explained here.