CODEWITHSUNDEEP
pythondjango
Aylen
Aylen

Reputation: 3554

Django query - Retrieve objects that don't have other object pointing to them

I've got a model named String that looks something like this:

class String(models.Model):
    text = models.TextField()
    language = models.ForeignKey(Language, default=get_english)
    original_string = models.ForeignKey('self', null=True, blank=True)

The default language for the strings is English, then, in the same table on the database, I have the translated strings with different languages, each one pointing to the corresponding string in English through original_string.

What I need is to retrieve the strings in English that DON'T have associated strings in another language, i.e., that don't have a translation.

Right now I'm iterating over all string in English and appending the ones I need to a list, like:

translatable_strings = String.objects.filter(language__name="English")

strings = []

for string in translatable_strings:
    if not String.objects.filter(language=translator_lang,
                                 original_string=string).exists():
        strings.append(string)

But I think that's a pretty nasty piece of code. Isn't there a way to make this in a single query?

Upvotes: 3

Views: 164

Answers (2)

Aamir Rind
Aamir Rind

Reputation: 39659

Try this

String.objects.filter(language__name="English", original_string__isnull=True)

Upvotes: 1

dani herrera
dani herrera

Reputation: 51655

First condition: language is english

Second condition: not exists another string that references it.

String.objects.filter( language = 'english', 
                       string__original_string__isnull = True )

A foreignkey backward reference is needed.

Upvotes: 4

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