Django error - matching query does not exist

244,384

Solution 1

your line raising the error is here:

comment = Comment.objects.get(pk=comment_id)

you try to access a non-existing comment.

from django.shortcuts import get_object_or_404

comment = get_object_or_404(Comment, pk=comment_id)

Instead of having an error on your server, your user will get a 404 meaning that he tries to access a non existing resource.

Ok up to here I suppose you are aware of this.

Some users (and I'm part of them) let tabs running for long time, if users are authorized to delete data, it may happens. A 404 error may be a better error to handle a deleted resource error than sending an email to the admin.

Other users go to addresses from their history, (same if data have been deleted since it may happens).

Solution 2

Maybe you have no Comments record with such primary key, then you should use this code:

try:
    comment = Comment.objects.get(pk=comment_id)
except Comment.DoesNotExist:
    comment = None

Solution 3

You can use this:

comment = Comment.objects.filter(pk=comment_id)

Solution 4

You may try this way. just use a function to get your object

def get_object(self, id):
    try:
        return Comment.objects.get(pk=id)
    except Comment.DoesNotExist:
        return False
Share:
244,384
Chris P
Author by

Chris P

Updated on April 02, 2022

Comments

  • Chris P
    Chris P almost 2 years

    I finally released my project to the production level and suddenly I have some issues I never had to deal with in the development phase.

    When the users posts some actions, I sometimes get the following error.

    Traceback (most recent call last):
    
      File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py", line 111, in get_response
        response = callback(request, *callback_args, **callback_kwargs)
    
      File "home/ubuntu/server/opineer/comments/views.py", line 103, in comment_expand
        comment = Comment.objects.get(pk=comment_id)
    
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 131, in get
        return self.get_query_set().get(*args, **kwargs)
    
      File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 366, in get
        % self.model._meta.object_name)
    
    DoesNotExist: Comment matching query does not exist
    

    What really frustrates me is that the project works fine in the local environment and furthermore, the matching query object DOES exist in the Database.

    Now I am suspecting that the user is accessing the Database when it's reserved to other users, but there's no way to prove my argument nor I have any solution to it.

    Does anybody had this kind of issue before? Any suggestions on how to resolve this issue?

    Thank you very much for your help in advance.

    EDIT: I have manually queried the database using the same information retrieved from the server error email I received. I was able to hit the entry without any issue. Furthermore, it seems like the exact same behavior the user performed does not raise any issue most of the time, but rather in some (which is yet unknown) cases. In conclusion, it definitely is not an issue with the missing entry in the database.

    • karthikr
      karthikr over 10 years
      Clearly, it is a data issue: comment = Comment.objects.get(pk=comment_id) verify the id exists in the database
    • Ricola3D
      Ricola3D over 10 years
      "python manage.py sqlall" will generate the SQL corresponding to your models. Check if it corresponds to the DB schema SQL. If working with PostgreSQL for example, it can also be an issue of sequence. In conclusion: can you bring more information about your environment (SQDB, DB, corresponding table in DB and code in models.py, ...) ?
    • Chris P
      Chris P over 10 years
      @Ricola3D Hello Ricola, I am currently using MySql DB hosting it from Amazon EC2 instance. And I am using the built in Django Comment for the time being. In the meantime, I'll try to run the sqlall command you suggested. Thank you.
  • Yuji 'Tomita' Tomita
    Yuji 'Tomita' Tomita over 10 years
    +1 on long running tabs. 404 via old tabs happens to me a lot.
  • Chris P
    Chris P over 10 years
    Thank you Chris for your suggestion. What really bothers me is that when I query the MySql database manually (using the error information I received from the server) I do hit the correct entry without any issue. Also, the same action sometimes throw DoesNotExist exception but works most of the other times. It doesn't seem like the issue with the missing entry in the database :(
  • christophe31
    christophe31 over 10 years
    I may have fewer users, but with postgres I never had this kind of problems. We really don't have many information, your database don't have slave/master clustering? You don't use cache on querysets?
  • Chris P
    Chris P over 10 years
    @christophe31 So I haven't yet really implemented any kind of DB performance optimization nor back up methods such as slave/master clustering or caching on querysets. I guess I'll implement those features and see if the problem persists.
  • christophe31
    christophe31 over 10 years
    I thaught about it as possible problems source not as possible problems solutions ^^. As you can't reproduce the bug, I would suggest a stupid solution. try catch the error, re get in the catch after sleeping a second and logging.
  • christophe31
    christophe31 over 10 years
    Also you may add this in the catch: from django.db import connection, connection.connection.close(), connection.connection = None to try to reset db connection and start from a new one.
  • Jay Modi
    Jay Modi over 7 years
    Well, If there is specific object you want then you can not use filter as It may return empty list If query does not match. And when It matched then you gotta use first object from the list.
  • Mike 'Pomax' Kamermans
    Mike 'Pomax' Kamermans over 5 years
    Presumably that's the point: use filter and test whether the result has zero or one entries, instead of generating an exception?
  • ron_g
    ron_g almost 5 years
    Worth noting that Model.objects.filter will return a Queryset, whereas Model.objects.get will return an object. If the object doesn't exist, the former will return an empty queryset, the latter will result in a Model.DoesNotExist error.
  • steezeburger
    steezeburger over 4 years
    Comment.objects.filter(pk=comment_id).first() will return None if no records are found.
  • Love Putin
    Love Putin almost 4 years
    Best option in such cases. Instead of throwing 404 at the user, catch the error and display a nice preconfigured message. No heart burns.
  • snh_nl
    snh_nl over 3 years
    How would it work here? def previous_job(self): return self.get_previous_by_start_dt(brand=self.brand, status='finished') or None dont know how to implement the try catch here
  • Ali Husham
    Ali Husham almost 3 years
    how to do like ` f (can_not_get Comment.objects.get(pk=comment_id)): print('not avaliable') `
  • christophe31
    christophe31 almost 3 years
    @ali-al-karaawi c = Comment.objects.filter(pk=c_id).first(), then c is either your comment or None so you can if it.
  • Nwawel A Iroume
    Nwawel A Iroume almost 2 years
    the asker doesn't need to create a comment