Django queryset模型在字段中应用函数

Question

It is possible simulate this query SQL in Django models using function in field in where clause.

My Query SQL

SELECT id, name, email
  FROM students where md5(cast(id as text)) = 'e4da3b7fbbce2345d7772b0674a318d5';

My Django model.

class Students(models.Model):
    name = models.CharField(max_length=50)
    email = models

Methods in Django - Value of where_filter is a MD5 of value field id / pk .

where_filter = 'e4da3b7fbbce2345d7772b0674a318d5'

Students.objects.get(pk=where_filter)
Students.objects.filter(pk=where_filter)

Thanks.

Answer 1

You can do this with a custom Transform class.

Something like:

class Md5Value(Transform):
    lookup_name = 'md5'
    output_field = CharField()

    def as_sql(self, compiler, connectino):
        lhs, params = compiler.compile(self.lhs)
        return "MD5(cast(%s as text))"  % lhs, params

AutoField.register_lookup(MD5Value)

Now you can do:

where_filter = 'e4da3b7fbbce2345d7772b0674a318d5'

Students.objects.get(pk__md5=where_filter)