Question

Context: Foo is a class that has a foreignKey field pointing to a Bar object. Several Foos may refer to the same Bar. (Many to one)

I need to reference several fields of a Foo object’s foreignkey (Bar.field and Bar.field2), but it seems that each time I do so it runs a separate query.

As a result, referencing these fields can take forever.

Is there a way to get all the Bar objects in a single query? Or is there a better way to speed it up?

foo_list = Foo.objects.filter(params) # takes 0.001 sec, returns 10k objects

result = []

for f in foo_list:

    # this part takes 40 seconds due to the huge number of queries 
    bar = f.bar # Foo contains a foreignKey reference to the Bar class

    result.append({
        "field": f.field,
        "barField": bar.barField,
        "barField2": bar.barField2,

        # this way was even worse
        # "barField": f.bar.barField,
        # "barField2": f.bar.barField2, 
    })

Answer 1

foo_list = Foo.objects.filter(params).select_related()

does the job. The rest of the code would remain the same, but

for f in foo_list:
    f.bar

would use the cached objects