prefetch_related（）在Django中的ForeignKey反向查找？

Question

我有两个型号：

class Company(models.Model): 
    ... 

class Supplier(models.Model): 
    company = models.ForeignKey(Company, null=True, related_name="suppliers") 

如何获得所有与公司及其相关供应商？

我已经试过：

Company.objects.prefetch_related('suppliers') 
Company.objects.prefetch_related('supplier_set') 
Company.objects.prefetch_related('suppliers').all() 
... 

我做错了吗？

谢谢

Answer 1

prefetch_related just adds the SQL query得到供应商，这样，当你做company.suppliers.all()你不招致另一个SQL击中的Company.objects.all()顶部。您可以通常访问以下供应商：

companies = Company.objects.all().prefetch_related('suppliers') 

for company in companies: 
    # Does not require a new SQL query 
    suppliers = company.suppliers.all()