計數內多對多領域的Django

Question

假設我有以下型號：

class Analysis(Model): 
    experts = ManyToManyField(Expert, 
           related_name='analysis', 
           through='AnalysisExpert') 


class AnalysisExpert(Model): 
    analysis = ForeignKey(Analysis) 
    expert = ForeignKey(Expert 

    questions = ManyToManyField(Question, through='ExpertQuestion') 

class ExpertQuestion(Model): 
    expert = ForeignKey(AnalysisExpert, related_name="expert_comparisons") 

    question = ForeignKey('Question') 

它看起來像我有嵌套ManyToManyField。分析 - >專家 - >問題

什麼是計算特定分析問題數量的最有效方法？

Answer 1

您可以使用values_list計算單個分析對象的問題數量。

analysis_obj.experts.all().values_list("question").count() 

上面的查詢測試，下面的模型：

class Question(models.Model): 
    question = models.CharField(max_length=50) 


class Expert(models.Model): 
    question = models.ManyToManyField(Question, 
           related_name='questions') 

class Analysis(models.Model): 
    experts = models.ManyToManyField(Expert, 
        related_name='analysis')