CODEWITHSUNDEEP
djangopython-3.xdjango-queryset
Rex
Rex

Reputation: 15

Annotating a queryset with objects from a different "filter" queryset

If you're filtering a queryset using values from a different queryset, what is the best way to annotate the "filter" value onto the original queryset?

For example, below I have a simGrants QS that I'm filtering using the simKeys QS. When a match is found, I'd like to append the matching simKeys cosine score to the simGrants object.

The database is fairly large so I'm looking to find the most computationally efficient way to do this. 

Simkeys =similarity_matrix.objects.filter(y_axis__in=profiles).filter(cosine_score__gt=0)
simGrants = Grant.objects.filter(indexKey__in=simKeys)

Upvotes: 1

Views: 180

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476557

You can annotate your Grant object with the fields from the related model with an F-expression [Django-doc]. This results in a query that looks like:

from django.db.models import F

Grant.objects.annotate(
    cosine_score=F('similarity_matrix__cosine_score')
).filter(
    similarity_matrix__y_axis__gt=0,
    similarity_matrix__cosine_score__gt=0
)

The Grant objects that arise from this queryset will have an extra attribute cosine_score that is the cosine_score of the related similarity_matrix object.

Upvotes: 1

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