How to make uniques in Django Models? And also index a column in Django

Question

This is my simple Django database model. It's for a 5-star rating system.

class Rating(models.Model):
    content = models.OneToOneField(Content, primary_key=True)
    ip =  models.CharField(max_length=200, blank=True)
    rating = models.IntegerField(default=0)

As you can see, it is linked to "Content", which is the table for my documents. My question is:

How do I make content+ip unique...so that it multiple content is okay, but multiple content AND IP is not okay (do not want the user to rate twice).
How do I create a data-base index for content and ip...because I will always be selecting those (to compare if it is already in the database).

Why to use `CharField()` for IP instead of `IPAddressField()`? — Surya, Jan 04 '13 at 14:20

score 14 · Accepted Answer · edited Aug 08 '15 at 21:01

14

Regarding your first question: You should look at unique_together, since this could solve your issue.

class Rating(models.Model):
    content = models.OneToOneField(Content, primary_key=True)
    ip =  models.CharField(max_length=200, blank=True)
    rating = models.IntegerField(default=0)

    class Meta:
        unique_together= (('content', 'ip'),)

edited Aug 08 '15 at 21:01

JackDev

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answered Nov 25 '09 at 01:18

ikkebr

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it might be better to convert the IP into an `int` before storing, and use an `IntegerField`. it will use less space (im not sure why you've allocated 200 bytes to an IP address), and allow more query flexibility. you may also want to check out `django-ratings` (http://github.com/dcramer/django-ratings), which handles both anonymous and authenticated votes very well. – Carson Nov 26 '09 at 17:48

score 7 · Answer 2 · answered Nov 25 '09 at 03:36

BTW, if, as it appears from your terminology, you're using IP addresses as standing for users' identities, please don't -- it's a seriously horrible idea. Users coming in through their ISP will get their IPs changed at random times, so they might vote twice; users on a laptop connecting at various coffee shops, libraries, &c, will have always-varying IPs; users sharing a connection (e.g., apartment-mates), or even every single one of users coming in from a University campus, might get the same IP address via NAT, so only one will be able to vote... it's hard to think of any worse way to represent individuals' identities!-)

If your use of the name ip for your "user identity" field is accidental and has nothing to do with using IP addresses there, I apologize, but in that case please do rename that field!-)

An alternate idea is to use a cookie or LocalStorage. – R891 Aug 20 '16 at 01:07 — R891, Aug 20 '16 at 01:07

score 5 · Answer 3 · edited May 03 '11 at 15:38

5

About the indexes: you don't need to do anything for content, since it is a primary key, it will be indexed. For ip, just add db_index=True to the CharField constructor call:

ip = models.CharField(max_length=200, blank=True, db_index=True)

More information about db_index and other field options here

edited May 03 '11 at 15:38

Akseli Palén

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answered Nov 25 '09 at 02:07

Ned Batchelder

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Indexing a second field will not make that field unique with the primary key. – hughdbrown Nov 25 '09 at 14:22
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I wasn't answering the question about uniques. The second bullet in the question asks about indexing ip. – Ned Batchelder Nov 25 '09 at 14:47

score 4 · Answer 4 · answered Apr 04 '20 at 19:54

This is the answer for those who are using Django 3.0+.

It's better to use UniqueConstraint ( as per the docs ) for making uniques.

 class Rating(models.Model):
    ...

    class Meta:
        constraints = [ models.UniqueConstraint(fields=['content', 'ip'], name="unique-content-ip") ]
        indexes = [ models.Index(fields=['content', 'ip']) ]

And hence you can define multiple constraints & indexes.

score 0 · Answer 5 · answered Jul 28 '17 at 04:51

Please try this metha keyword: "unique_together"

    class PowerBoardSwitches(models.Model):
        id = models.AutoField(primary_key=True, verbose_name='Switch id')
        powerBoardId = models.ForeignKey(PowerBoardDevice, models.DO_NOTHING, db_column='powerBoardId', verbose_name='Power Board Id')
        powerBoardSwitchId = models.IntegerField()
        powerBoardSwitchStatus = models.IntegerField()
        createdOn = models.DateTimeField(auto_now_add=True, verbose_name='Created on date')
        updatedOn = models.DateTimeField(auto_now_add=True, verbose_name='Updated on date')

        class Meta:
            unique_together = (('powerBoardId', 'powerBoardSwitchId'), )

How to make uniques in Django Models? And also index a column in Django

5 Answers5