CODEWITHSUNDEEP
djangomany-to-manydjango-orm
Neil P
Neil P

Reputation: 33

Django: Find all values in a ManyToMany relationship where all elements of the related set match certain criteria

I have two models in a ManyToMany relationship. I want to get a subset of the first model for which every related model matches certain criteria.

Scenario: This is for a collaborative dictionary. A Word may have 0 or more Definitions. A Definition may be in a number of states: "complete", "in progress" or "abandoned". I am interested in finding all Words which have either no Definitions or only have "abandoned" Definitions.

class DefinitionState(Enum):
    COMPLETE = 0
    IN_PROGRESS = 1
    ABANDONED = 2

class Definition(models.Model):
    text = models.TextField()
    status = models.IntegerField()

class Word(models.Model):
    text = models.CharField(length=60)
    definitions = models.ManyToManyField(Definition, related="words")

spam = Word.objects.create(text="spam")
eggs = Word.objects.create(text="eggs")
bacon = Word.objects.create(text="bacon")
lobster = Word.objects.create(text="lobster")

spam_d1 = Definition.objects.create(
    text="Processed meat", 
    status=DefinitionState.COMPLETE
)
spam_d2 = Definition.objects.create(
    text="Unwanted email",
    status=DefinitionState.ABANDONED
)
spam.definitions.add(spam_d1)
spam.definitions.add(spam_d2)

eggs_d = Definition.objects.create(
    text="Laid by chickens",
    status=DefinitionState.COMPLETE
)
eggs.definitions.add(eggs_d)

bacon_d = Definition.objects.create(
    text="Part of a pig",
    status=DefinitionState.ABANDONED
)
bacon.definitions.add(bacon_d)

So I have four Words:

I want to write a query which will return (bacon, lobster) (in no particular order).

I can write the query to return lobster:

Word.objects.annotate(Count("definitions")).filter(definitions__count=0)

and I can identify which definitions are abandoned:

Definition.objects.filter(status=DefinitionState.ABANDONED)

but I can't figure out how to ask for Words whose Definitions are all ABANDONED.

Many thanks in advance

Upvotes: 3

Views: 111

Answers (1)

Nidal
Nidal

Reputation: 415

Words.objects.exclude(definitions__status__in=[COMPLETE, IN_PROGRESS])

Upvotes: 3

Related Questions