EF Core 3.0转换为SQL问题-EF Core内部或用户代码是否出错？

Question

尝试执行汇总查询以根据复杂的分组类型获得不同的计数。 “更清洁”的方式无法转换为SQL，“工作”的方式可转换为SQL。理想情况下，我希望采用“更清洁”的方法，因为它对我而言看起来更好。

为什么选择唯一计数在这里失败？

//我们要做的：（

        var uniqueExercises = details
            .GroupByWorkoutTypeThenWorkoutDateThenExerciseId(config.GroupByWorkoutType, config.TimePeriod)
            .Select(x => new
            {
                Date = x.Key.Date,
                WorkoutType = x.Key.WorkoutType,
                ExerciseCount = 1
            })
            .GroupBy(x => new
            {
                x.Date,
                x.WorkoutType
            })
            .Select(x => new
            {
                Date = x.Key.Date,
                WorkoutType = x.Key.WorkoutType,
                ExerciseCount = x.Sum(y => y.ExerciseCount)
            });

//从逻辑上讲有意义但翻译不正确

        var uniqueExercises = details
            .GroupByWorkoutTypeThenWorkoutDate(config.GroupByWorkoutType, config.TimePeriod)
            .Select(x => new
            {
                Date = x.Key.Date,
                WorkoutType = x.Key.WorkoutType,
                ExerciseCount = x.Select(x => x.Exercise.Id).Distinct().Count()
            });