Django comment framework: distinct () not working?

Question

Running different () in any field of the comment model always returns all records,

Comment.objects.values ​​('user'). Different ()

[{'user': 1}, {'user': 0}, {'user': 0}, {'user': 0}, {'user': 0}, {'user': 1}, { 'user': 1}, {'user': 1}, {'user': 1}]

Comment.objects.values ​​('ip_address'). Different ()

[{'ip_address': u'127.0.0.1'}, {'ip_address': u'192.168.0.180'}, {'ip_address': u'192.168.0.180'}, {'ip_address': u'192.168.0.180 '}, {' ip_address': u'192.168.0. 180 '}, {' ip_address': u'192.168.0.180 '}, {' ip_address': u'192.168.0.180 '}, {' ip_address': u'192.168.0.180 '}, {' ip_address': u ' 192.168.0.180 '}]

Why is this happening? Is there any way around this? Thanks!

ps: distinct () works fine in different types of user model fields during my test. Something special about the comment structure?

End Bit Thanks to everyone who answers this question, in combination with some reading, I get an opinion as follows:

• values ​​() affects the search fields in the SELECT part of the final sql (" values ​​() accepts optional positional arguments, * fields that indicate the names of the fields to which SELECT should be limited ")
• order_by () also adds its parameter to the SELECT part.

• using expression () in the search, sql will look like this:

  SELECT DISTINCT [fields1, fields2, fields3] FROM ... WHERE ...

  and field values ​​together decide if a record is unique. Fields can come from functions () or order_by () in the search.

• Thus, order_by () adds some undesirable effects in combination with distinct (), the fields specified in order_by also take into account, the record is unique

• The default comment for Django has a hidden order_by parameter, which creates the whole problem. Any model has a hidden order_by when returning qs can cause the same problem.

• The way to solve the problem is to add an empty order_by () at the end of the search, which removes the default order_by.

Answer 1

Comment.objects.values('user').distinct().order_by() 

Answer 2

I have not confirmed that this is the reason, but the Comment model has a default order, which affects the distinct() method:

 In [1]: print Comment.objects.values('ip_address').distinct().query SELECT DISTINCT "django_comments"."ip_address", "django_comments"."submit_date" FROM "django_comments" ORDER BY "django_comments"."submit_date" ASC 

This is a documentary function .

Now, how can it be that two comments have exactly the same timestamp? I suppose you are using MySQL which does not support anything less than a second.

And if you want to get rid of the default order, just do:

 Comment.objects.order_by().values('ip_address').distinct()