CODEWITHSUNDEEP
djangodjango-models
anand
anand

Reputation: 25

2 OneToOneField defined for two tables. One got deleted but not other

I have defined two OneToOneFields in my model as below:

class StudentCrossMap(models.Model):
    rfId = models.OneToOneField(StudentDailyTrans)
    studentId = models.OneToOneField(StudentMaster)

When I apply delete on the model above giving rfId, the entry related to it in StudentDailyTrans gets deleted, BUT the one in StudentMasterdid not gets removed.

Ideally, if I am deleting the object from StudentCrossMap it should not be deleting the entries from mapped tables as those tables are not dependent on StudentCrossMap table.

Please advise if I am doing something wrong.

*Edit: Related tables

class StudentDailyTrans(models.Model):
    rfId = models.CharField(max_length=30, primary_key=True)
    schoolId = models.ForeignKey(SchoolMaster, on_delete=models.CASCADE, db_index=False)
    fromTime = models.DateTimeField(null=True)
    toTime = models.DateTimeField(null=True)
    totalSwipeInstance = models.IntegerField(default=0)
    lastUpdateTs = models.DateTimeField(auto_now=True)

class StudentMaster(models.Model):
    studentId = models.IntegerField(primary_key=True)
    schoolId = models.ForeignKey(SchoolMaster, on_delete=models.CASCADE)
    parentId = models.ForeignKey(ParentMaster, on_delete=models.CASCADE)

class SchoolMaster(models.Model):
    schoolId = models.IntegerField(primary_key=True)
    subsStrtDt = models.DateTimeField(default=timezone.now)

class ParentMaster(models.Model):
    parentId = models.AutoField(primary_key=True)
    parentName = models.CharField(max_length=20, default='parent')

Upvotes: 1

Views: 121

Answers (1)

e4c5
e4c5

Reputation: 53774

If I have understood what you have posted correctly, you are better off with a design like this.

class Student(models.Model):
    id = models.IntegerField(primary_key=True)
    school = models.ForeignKey(SchoolMaster, on_delete=models.CASCADE)
    parent = models.ForeignKey(ParentMaster, on_delete=models.CASCADE)
    rf = models.CharField(max_length=30, primary_key=True)

This is essentially, your old StudentMaster model. I have renamed it to Student. I have also renamed the field names to comply with the usual django naming convention (school instead of school_id for the foreign key)

Now you can delete StudentDailyTrans and StudentCrossMap we are saving the same data more efficiently and yet without redundancy. And that eliminates the problem you asked about!!

You will agree with me that the code is a lot more readable.

Upvotes: 2

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