Filtering model instance's m2m field to exactly match another m2m field or list

Using Django Using the ORM
3

On Postgres the following should work in a constant number of queries (2).

# Keep a reference to foo and bar options with outer references so they can be reused.
foo_options = Foo.options.through.objects.filter(
    foo_id=OuterRef("pk")
).values("option_id")
bar_options = Bar.options.through.objects.filter(
    bar_id=OuterRef(OuterRef("pk"))
).values("option_id")
bars = Bar.objects.annotate(
    # Accumulate all the foo ids
    matching_options_foo_pks=ArraySubquery(
        Foo.objects.filter(
            # All the foo with no set difference between foo and bar options.
            ~Exists(
                foo_options.difference(bar_options)
            ),
            # ... and not difference between bar and foo options (both directions)
            ~Exists(
                bar_options.difference(foo_options)
            ),
        ).values("pk")
    )
)
# Retrieve all matching foos across all bars in a single query a bit
# like prefetch related does.
matching_foos = Foo.objects.in_bulk(
    set(itertools.chain.from_iterable(
        bar.matching_options_foo_pks for bar in bars
    ))
)
for bar in bars:
    foo_matches = [
        matching_foos[foo_pk]
        for foo_pk in bar.matching_options_foo_pks
    ]

This should generate SQL of the form

SELECT
    bar.*,
   ARRAY(
       SELECT foo.id
       FROM foo
       WHERE (
           NOT EXISTS (
               SELECT option_id FROM foo_options WHERE foo_options.foo_id = foo.id
               EXCEPT
               SELECT option_id FROM bar_options WHERE bar_options.bar_id = bar.id
           )
           AND NOT EXISTS (
               SELECT option_id FROM bar_options WHERE bar_options.bar_id = bar.id
               EXCEPT
               SELECT option_id FROM foo_options WHERE foo_options.foo_id = foo.id
           )
       )
   ) matching_options_foo_pks
FROM bar