[英]Fast filter on related fields in django
I have 2 models in my django project. 我的django项目中有2个模型。
ModelA(models.Model):
id = models.AutoField(primary_key=True)
field1 = ...
~
fieldN = ...
ModelB(models.Model):
id = models.AutoField(primary_key=True)
a = models.ForeignKey(A, on_delete=models.CASCADE)
field1 = ...
~
fieldN = ...
Here I have one-to-mane relation A->B. 在这里,我有一对一的关系A-> B. Table A has around 30 different fields and 10.000+ rows and table B has around 15 and 10.000.000+ rows. 表A有大约30个不同的字段和10.000+行,表B有大约15和10.000.000+行。 I need to filter firstly by the several ModelA
fields and then for each of the filtered ModelA
row/object get related ModelB
objects and filter them by several fields. 我需要首先通过几个ModelA
字段进行过滤,然后为每个过滤的ModelA
行/对象获取相关的ModelB
对象,并按几个字段过滤它们。 After that I need to serialize them in JSON where all ModelB
packed in one field as array. 之后我需要在JSON中序列化它们,其中所有ModelB
在一个字段中打包为数组。
Is it possible to perform this around the 1-3 second? 是否有可能在1-3秒左右执行此操作? If yes, what is the best approach? 如果是,最好的方法是什么?
I use PostgreSQL. 我使用PostgreSQL。
EDIT: 编辑:
Now I am doing it like chain .filter()
on simple ModelA
fields and then iterate over resulted QuerySet
and get set of ModelB
for each ModelA
instance,but i suspect, that the second part of this solution will slow down whole process, so I suppose there is a better way to do it. 现在,我在简单的ModelA
字段上执行链接.filter()
,然后遍历结果QuerySet
并为每个ModelA
实例获取ModelB
集,但我怀疑,此解决方案的第二部分将减慢整个过程,所以我假设有更好的方法来做到这一点。
It may be faster to do a query like this: 执行这样的查询可能会更快:
model_a_queryset = ModelA.objects.filter(field=whatever)
model_b_queryset = ModelB.objects.filter(a__in=model_a_queryset)
Because Django does lazy queryset evaulation, this will only result in one hit to the database. 因为Django执行了懒惰的查询集评估,所以这只会导致数据库的一次命中。
As an aside, there is no need to define id = Autofield
fields on your models. 另外,您无需在模型上定义id = Autofield
字段。 Django includes them by default. Django默认包含它们。
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