Django ORM在循环中过滤SUM不同的相关对象

Question

我有以下型号：

    class Developer(models.Model):
        name = models.CharField(max_length=100)

    class Skill(models.Model):
        code = models.CharField(max_length=30)

    class Experience(models.Model):
        date_from = models.DateField(blank=True, null=True)
        date_to = models.DateField(blank=True, null=True)
        developer = models.ForeignKey(Developer, related_name='experience', 
        on_delete=models.CASCADE)
    
    class SkillExperience(models.Model):
        skill = models.ForeignKey(Skill, on_delete=models.CASCADE, related_name='skill_experience')
        experience = models.ForeignKey(Experience, on_delete=models.CASCADE, related_name='skill_experience')
        years_experience = models.IntegerField()

我知道，对于单个查询，要让拥有至少 5 年 Python 经验的开发人员，我可以这样做：

Developer.objects.filter(
    experience__skill_experience__skill__code='Python'
).annotate(
    total_years=Sum('experience__skill_experience__years_experience')
).filter(
    total_years__gte=5
)

但是，如果我处于技能循环中并且需要检查 OR，那么如何进行操作，所以假设循环这个数组：[{code: 'python', years_experience: 5}, {code: 'node' , years_experience: 2}] 我需要返回拥有 5 年 Python 经验或 2 年节点经验的开发人员？

Answer 1

我认为最简单的方法是确定所有技能的总和，然后检查其中至少一项是否满足约束条件，因此：

# since Django-2.0

from django.db.models import Q, Sum

# sample data
data = [
    {code: 'python', years_experience: 5},
    {code: 'node', years_experience: 2}
]

annotates = {
    f'total_years_{i}': Sum(
        'experience__skill_experience__years_experience',
        filter=Q(experience__skill_experience__skill__code=di['code'])
    ) for i, di in enumerate(data)
}

qs = Q(
    *[(f'total_years_{i}__gte', di['years_experience']) for i, di in enumerate(data)],
    _connector=Q.OR
)

developers = Developer.objects.annotate(
    **annotates
).filter(
    qs    
)

作为奖励，developers 中的Developer 对象将具有.total_years_0、.total_years_1 等属性，用于包含该技能年数总和的列表中的每个技能。