python - Django:可查询的计算字段

Question

是否有一种“最佳”方法来执行可查询的计算字段？

例如:

from django.db import models

class Person(models.Model):
    given_name = models.CharField(max_length=30)
    family_name = models.CharField(max_length=30)

    NAME_ORDER_CONVENTION_CHOICES = (
        # "Eastern" name order: family name followed by given name
        ('E', 'Eastern'),
        # "Western" name order: given name followed by family name
        ('W', 'Western')
    )

    name_order_convention = models.CharField(
        length=1, 
        choices=NAME_ORDER_CONVENTION_CHOICES,
    )

    @property
    def full_name(self):
        """
        Return full name, calculated on the basis of given name,
        family name and name order convention.
        """
        template = "{} {}"
        if self.name_order_convention == "W":
            return template.format(self.given_name, self.family_name)
        return template.format(self.family_name, self.given_name)

这使您能够获取任何Person的full_name，但是如果您想根据全名进行数据库查询，则需要编写查询隐式了解如何计算此属性。这似乎违反了 DRY，因为不再有任何中心位置可以更改计算字段的计算方式 - 您必须在任何地方更改 full_name 属性它基于 full_name 工作原理的隐式知识进行查询。

我能想到的主要替代方案是重写 save() 方法以在每次更新时更新这些字段。

from django.db import models

class Person(models.Model):
    given_name = models.CharField(max_length=30)
    family_name = models.CharField(max_length=30)

    NAME_ORDER_CONVENTION_CHOICES = (
        ('E', 'Eastern'),
        ('W', 'Western')
    )

    name_order_convention = models.CharField(
        length=1, 
        choices=NAME_ORDER_CONVENTION_CHOICES,
    )

    # Computed fields
    full_name = models.CharField(max_length=60)

    def _calculate_full_name(self):
        template = "{} {}"
        if self.name_order_convention == "W":
            self.full_name = template.format(self.given_name, self.family_name)
        else:
            self.full_name = template.format(self.family_name, self.given_name)

    def save(self, *args, **kwargs):
        self._calculate_full_name()
        super(Model, self).save(*args, **kwargs)

对于我可能缺少的可查询计算字段，是否有一个通用的“最佳实践”解决方案？

Answer 1

我可以看到的一种方法:在数据库中创建 View ，并使用连接的全名而不是django中的托管模型来用于查询(Person模型也应该存在于增删改查操作):

查看(postgresql)

CREATE OR REPLACE VIEW appname_viewperson AS 
    SELECT id,
        given_name,
        family_name,
        given_name || ' ' || family_name AS full_name,
    FROM appname_person

非托管模型:

class ViewPerson(models.Model):
    given_name = models.CharField(max_length=30)
    family_name = models.CharField(max_length=30)
    full_name = models.CharField(max_length=60)

    class Meta:
        managed = False