is it safe to refactor my django models?

Question

My model is similar to this. Is this ok or should I make the common base class abstract? What are the differcenes between this or makeing it abstract and not having an extra table? It seems odd that there is only one primary key now that I have factored stuff out.

class Input(models.Model):
        details = models.CharField(max_length=1000)
        user = models.ForeignKey(User)
        pub_date = models.DateTimeField('date published')
        rating = models.IntegerField()

        def __unicode__(self):
            return self.details

    class Case(Input):
        title  = models.CharField(max_length=200)
        views = models.IntegerField()

    class Argument(Input):
        case = models.ForeignKey(Case)
        side = models.BooleanField()

is this ok to factor stuff out intpu Input? I noticed Cases and Arguments share a primary Key.

like this:

    CREATE TABLE "cases_input" (
        "id" integer NOT NULL PRIMARY KEY,
        "details" varchar(1000) NOT NULL,
        "user_id" integer NOT NULL REFERENCES "auth_user" ("id"),
        "pub_date" datetime NOT NULL,
        "rating" integer NOT NULL
    )
    ;
    CREATE TABLE "cases_case" (
        "input_ptr_id" integer NOT NULL PRIMARY KEY REFERENCES "cases_input" ("id"),
        "title" varchar(200) NOT NULL,
        "views" integer NOT NULL
    )
    ;
    CREATE TABLE "cases_argument" (
        "input_ptr_id" integer NOT NULL PRIMARY KEY REFERENCES "cases_input" ("id"),
        "case_id" integer NOT NULL REFERENCES "cases_case" ("input_ptr_id"),
        "side" bool NOT NULL
    )

Answer 1

From: django web site

Abstract base classes are useful when you want to put some common information into a number of other models. You write your base class and put abstract=True in the Meta class. This model will then not be used to create any database table. Instead, when it is used as a base class for other models, its fields will be added to those of the child class.