I know there is already a similar question, but I think my case is a bit more complicated because I have a different entry point.
These are my models:
class m_Interaction(models.Model):
fk_ip = models.ForeignKey('m_IP', related_name="interactions")
class m_User(models.Model):
name = models.CharField(max_length=200)
class m_IP(models.Model):
fk_user = models.ForeignKey('m_User', related_name="ips" )
class m_Feature(models.Model):
name = models.CharField(max_length=200)
m2m_interaction = models.ManyToManyField(m_Interaction, related_name='features', through='m_Featurescore')
class m_Featurescore(models.Model):
score = models.FloatField(null=False)
fk_interaction = models.ForeignKey(m_Interaction, related_name='featurescore')
fk_feature = models.ForeignKey(m_Feature, related_name='featurescore')
I start with m_User, follow the reverse relationship over m_IP to the Interactions (m_Interaction). Then I want to get every m_Featurescore.score for each Interaction for a specific instance of m_Feature.
My working query to access at least all interactions in a performant way:
m_User.objects.all().prefetch_related('ips__interactions')
But I can't figure out the correct 'prefetch_related'-statement to access the m_Featurescore.score like this
db_obj_interaction.featurescore.get(fk_feature=db_obj_feature).score
without making a lot of queries.
I already tried almost all combinations of the following:
'ips__interactions__features__featurescore'
Any suggestions?
I found the answer to my own question with the help of noamk in the comments:
I didn't consider that the get()-method in db_obj_interaction.featurescore.get(fk_feature=db_obj_feature).score will issue a new query everytime it's called (it's kinda obvious now).
Therefore I simply restructured my code and now I don't need get() anymore and can use the benefit of the prefetch.
If somebody still needs to filter the Prefetch()-object should be used as suggested by noamk