Django: Unique IDs for each sub-model of a Model-CodePudding

I'm fairly new to Django, but I believe my question is more towards designing databases regardless of the framework or platform.

Let me explain using following quick pseudo. I have following two models:

class Issue(models.Model):
    title = models.CharField(max_length=60)
    status = models.IntegerField(choices=Status.choices, default=Status.OPEN)
    ...

class Comment(models.Model):
    issue = models.ForeignKey(Issue, on_delete=models.CASCADE, related_name="comments")
    text = models.TextField()
    ...

In my web app, I'm building a collection of Issues. Each issue is assigned a django's auto-generated unique ID number (pk), which is perfect. And for each issue there is a property comments which holds a collection of comments specific to this issue.

Each comment also has a system-generated unique ID, but the sequence of this ID is not specific to the Issue model. Means if I create 3 comments in Issue #1 (comment #1, #2, #3), and then I create a comment under Issue #2, that comment's ID is set as #4 instead of #1.

I understand that this is the way the data models are defined. What I would like to have is that whenever a new issue is created and a comment added, its ID should start from 1. I cannot define comment IDs manually by incrementing over the previous comment ID because the web app will allow users to delete the comments too. So if there are 3 comments under an issue and the last comment #3 is deleted, the next time a comment is added it should be given a unique ID #4.

Any suggestions how do I go about implementing a robust solution to this? TIA

EDIT: The purpose of restarting comment ID from 1 each time is that the comment ID is to be displayed in the HTML against each comment. It will be used by the users for referencing purpose.

CodePudding user response：

It looks to me like you are trying to keep track of the number of comments per issue. This can be done using Issue.comments.count() or use a cached property that is updated every time there is a new comment. If you want to know the order in which the comments were added, you can add a created_at field and use it for ordering in your queries as follows issue.comments.order_by('created_at').

CodePudding user response：

add created_at datetimeField in comment table and sort by created_at to return query

CodePudding user response：

You can make use of forloop.counter

Give this a try

{% for comment in issue.comments.all %}
    No: {{ forloop.counter }}
    {{ comment.text }}
{% endfor %}

Update:

to fix re-numbering on the deletion of a comment, the best thing you can do is to perform a soft-deletion

{% for comment in issue.comments.all %}

    {% if comment.is_active %}
        No: {{ forloop.counter }}
        {{ comment.text }}
     {% endfor %}

{% endfor %}

add an is_active boolean filed to the Comment model

class Comment(models.Model):
    ...
    is_active = models.BooleanField(default=True)

then instead of deleting the Comment object, set is_active to False, which will prevent renumbering issues in the template

CodePudding user response：

What I would do is probably something a bit different. I would add some kind of hierarchy filed to the Comment model. (and not play around with the Django auto generated id's).

class Comment(models.Model):
    issue = models.ForeignKey(Issue, on_delete=models.CASCADE, related_name="comments")
    text = models.TextField()
    hierarchy = models.IntegerField() 
...

This way the comments by id will look like this:

Issue1 - C1, C2, C3 ... C1-h1, C2-h2, C3-h3 (where h is the hierarchy)
Issue2 - C4, C5, C6 ... C4-h1, C5-h2, C6-h3.

This way you will be able to show on the frontend the hierarchy (not the id), and when you will delete a comment (you mentioned this), you will be able to continue with h4. (by my understanding this was your intended purpose).

Let me know if I should clarify more.