Query with RawAnnotation

raw_annotation_example.py

class RawAnnotation(RawSQL):
    """
    RawSQL also aggregates the SQL to the `group by` clause which defeats the purpose of adding it to an Annotation.
    """
    def get_group_by_cols(self):
        return []

# The Query
q = MyModel.objects.values('some_fk_id').annotate(
    avg_duration=Avg('duration'),
    perc_90_duration=RawAnnotation('percentile_disc(%s) WITHIN GROUP (ORDER BY duration)', (0.9,)),
)

print q.query

# SELECT "some_fk_id",
#        AVG("duration") AS "avg_duration",
#        (percentile_disc(0.9) WITHIN
#         GROUP (
#                ORDER BY duration)) AS "perc_90_duration"
# FROM "mymodel"
# GROUP BY "some_fk_id"