I'm trying to get the count of the number of times a player played each week like this:
player.game_objects.extra(
select={'week': 'WEEK(`games_game`.`date`)'}
).aggregate(count=Count('week'))
But Django complains that
FieldError: Cannot resolve keyword 'week' into field. Choices are: <lists model fields>
I can do it in raw SQL like this
SELECT WEEK(date) as week, COUNT(WEEK(date)) as count FROM games_game
WHERE player_id = 3
GROUP BY week
Is there a good way to do this without executing raw SQL in Django?
You could use a custom aggregate function to produce your query:
WEEK_FUNC = 'STRFTIME("%%%%W", %s)' # use 'WEEK(%s)' for mysql
class WeekCountAggregate(models.sql.aggregates.Aggregate):
is_ordinal = True
sql_function = 'WEEK' # unused
sql_template = "COUNT(%s)" % (WEEK_FUNC.replace('%%', '%%%%') % '%(field)s')
class WeekCount(models.aggregates.Aggregate):
name = 'Week'
def add_to_query(self, query, alias, col, source, is_summary):
query.aggregates[alias] = WeekCountAggregate(col, source=source,
is_summary=is_summary, **self.extra)
>>> game_objects.extra(select={'week': WEEK_FUNC % '"games_game"."date"'}).values('week').annotate(count=WeekCount('pk'))
But as this API is undocumented and already requires bits of raw SQL, you might be better off using a raw query.