Django 注释不适用于 order_by

Question

我想获取 MyModel order_by('-end_date') 的最后 100 条记录，并对不同的获胜者类型进行 SUM 注释

MyModel.objects.all()[:100].order_by('-end_game_time').values('winner').annotate(total=Count('winner'))

结果查询如下，我没有预期的组

<QuerySet [{'winner': 3, 'total': 1}, {'winner': 15, 'total': 1}, 'total': 1}, {'winner': 3, 'total': 1}, {'winner': 5, 'total': 1}, {'winner': 15, 'total': 1}, {'winner': 5, 'total': 1}, {'winner': 3, 'total': 1}, '...(remaining elements truncated)...']>

生成的查询就像

SELECT "game_mymodel"."winner", COUNT("game_mymodel"."winner") AS "total" FROM "game_mymodel" GROUP BY "game_mymodel"."winner", "game_mymodel"."end_game_time" ORDER BY "game_mymodel"."end_game_time" DESC LIMIT 100

但是当我没有 order_by 时，结果与我预期的一样

MyModel.objects.all()[:100].values('winner').annotate(total=Count('winner'))
Out[52]: <QuerySet [{'winner': 5, 'total': 43}, {'winner': 1, 'total': 2}, {'winner': 15, 'total': 51}, {'winner': 2, 'total': 42}, {'winner': 3, 'total': 43}]>

和生成的查询group_by部分不同

SELECT "game_mymodel"."winner", COUNT("game_mymodel"."winner") AS "total" FROM "game_mymodel" GROUP BY "game_mymodel"."winner" LIMIT 100

Answer 1

据我所知，在单个查询中不可能实现您想要做的事情，您在 SQL 中想要的是：

SELECT "game_mymodel"."winner", COUNT("game_mymodel"."winner") AS "total" FROM "game_mymodel" GROUP BY "game_mymodel"."winner" ORDER BY "game_mymodel"."end_game_time" DESC LIMIT 100

这不是一个有效的 sql 查询，因此您需要有一个子查询来选择 100 个元素，然后对它们应用聚合。

首先构建子查询：

top_100_games = MyModel.objects.order_by('-end_game_time')[:100].only('id').all()

然后在主查询中使用它：

MyModel.objects.filter(id__in=top_100_games).values('winner').annotate(total=Count('winner'))