优化Django-SQL查询

Question

我有3个模型。

class ShipmentPPTLMapping(models.Model): 
    pptl_id = models.CharField(max_length = 255) 
    shipment_id = models.ForeignKey('Shipment', related_name = 'pptls') 

class ShipmentBagSealMapping(models.Model): 
    bag_seal = models.CharField(max_length = 255) 
    status = models.CharField(max_length = 255, default = 'open') 
    shipment_id = models.ForeignKey('Shipment', related_name = 'bags') 



class Shipment(models.Model): 
    job_id = models.CharField(max_length = 255) 

我需要写过滤掉那些袋子from ShipmentBagSealMapping这是closed状态的查询，提供pptl_idfrom ShipmentPPTLMapping。

我有一个pptl_id在开始。因为我过滤了所有与此有关的货物，因为shipments_obj与ShipmentBagSealMapping有关，所以使用shipments_obj是我可以过滤掉封闭袋子的唯一方法。

shipment_pptl_mapping_obj_list = ShipmentPPTLMapping.objects.filter(pptl_id = pptl_id) 

然后我的shipment_pptl_mapping_obj_list周围循环来找到状态closed袋。

for shipment_pptl_mapping_obj in shipment_pptl_mapping_obj_list: 
    closed_bags = shipment_pptl_mapping_obj.shipment_id.bags.filter(status = 'closed') 
    #and then again another loop 
    for bags in closed_bags: 
     #something 

我怎样才能找到一切只是在1查询？

这是我的最终代码

shipment_pptl_mapping_obj_list = ShipmentPPTLMapping.objects.filter(pptl_id = pptl_id) #--> extend this 
for shipment_pptl_mapping_obj in shipment_pptl_mapping_obj_list: 
    closed_bags = shipment_pptl_mapping_obj.shipment_id.bags.filter(status = 'closed') 
    for bags in closed_bags: 
     #do something 

我想是这样的

closed_bags = Some Query 
for bags in closed_bags: 
    #do_something 

Answer 1

首先纠正你的机型，外键的字段名不应该包含在最终_id。这将导致许多问题和失望后

class ShipmentPPTLMapping(models.Model): 
    pptl_id = models.IntegerField() # if you id is Integer of course 
    shipment = models.ForeignKey('Shipment', related_name = 'pptls') 

class ShipmentBagSealMapping(models.Model): 
    bag_seal = models.CharField(max_length = 255) 
    status = models.CharField(max_length = 255, default = 'open') 
    shipment = models.ForeignKey('Shipment', related_name = 'bags') 



class Shipment(models.Model): 
    job_id = models.IntegerField(max_length = 255) 

二

closed_bags = Shipment.objects.filter(pptls__pptl_id__exact=pptl_id, status='closed') 

这应该可以解决你的问题