带参数的Django ManyToManyField过滤器？

Question

我有这样的模型：

class Category(Model): 
    ... 
    type = models.CharField(max_length=255, choices=settings.CATEGORIES) 

class Product(models.Model): 
    ... 
    categories = models.ManyToManyField(Category) 

我的类别列表，通过用户输入（格式任意）：

c = [<Category: G, type: producer>, <Category: L, type: producer>, <Category: Teen, type: age>, <Category: Man, type: sex>] 

现在我想有一个在类别有“G所有产品'或'L'类型'生产者'，'青少年'类型'年龄'和'人'类型'性'。我这样做，例如接下来的查询集：

Product.objects.filter(Q(categories=c[0])|Q(categories=c[1]), Q(categories=c[2]), Q(categories=c[3]) 

有这样的查询：

SELECT "shop_product"."id", "shop_product"."title", "shop_product"."description", 
"shop_product"."price", "shop_product"."code", "shop_product"."stored_count", 
"shop_product"."sold_count", "shop_product"."added_date" FROM "shop_product" 
INNER JOIN  "shop_product_categories" ON ("shop_product"."id" = 
"shop_product_categories"."product_id") WHERE 
(("shop_product_categories"."category_id" = 1 OR 
"shop_product_categories"."category_id" = 2) AND  
"shop_product_categories"."category_id" = 4 AND 
"shop_product_categories"."category_id" = 6) 

我至少有一个对象，适合这样的要求，但查询集返回任何内容。有什么建议？

Answer 1

您需要进行级联过滤，否则当前选择将返回所有具有值为1/2以及4和6的"shop_product_categories"."category_id"的产品...以下是一个将返回所需内容的示例查询集：

Product.objects.filter(categories__in=c[0:2]) 
       .filter(categories=c[2]) 
       .filter(categories=c[3]) 
       .distinct() 

哪像这样生成的SQL：

SELECT DISTINCT "test1_product"."id" FROM "test1_product" INNER JOIN "test1_product_categories" ON ("test1_product"."id" = "test1_product_categories"."product_id") 
    INNER JOIN "test1_product_categories" T4 
     ON ("test1_product"."id" = T4."product_id") 
    INNER JOIN "test1_product_categories" T6 
     ON ("test1_product"."id" = T6."product_id") 
WHERE ("test1_product_categories"."category_id" IN (1, 2) 
    AND T4."category_id" = 3 
    AND T6."category_id" = 4)