如何在 Django 2.2 模型中创建部分索引

Question

我在 Django 2.2 中有一个这样的模型

class Post(models.Model):
    class Meta:
        verbose_name = _('Post')
        verbose_name_plural = _('Posts')

    phone_number = models.CharField(max_length=11, verbose_name=_('Phone number'), db_index=True)

    token = models.CharField(unique=True, max_length=20, verbose_name=_('Token'), db_index=True)
 
    post_state = models.SmallIntegerField(choices=[
        (PostState.NEW, _('New')),
        (PostState.PUBLISHED, _('Published')),
        (PostState.ARCHIVED, _('Archive')),
        (PostState.REMOVED_BEFORE_PUBLISH, _('Removed before publish')),
        (PostState.REJECTED_AFTER_PUBLISH, _('Rejected after publish')),
    ], default=PostState.NEW, verbose_name=_('Post state'), db_index=True)

我希望我在 phone_number 上的索引和令牌基于 post_state 值是部分的，我知道如何使用 Postgres 中的 SQL 命令来做到这一点 shell 但我不知道如何在 Django 模型中做到这一点，所以它也进入了迁移文件。

Answer 1

所以我找到了这个问题的答案。

class Post(models.Model):
    class Meta:
        verbose_name = _('Post')
        verbose_name_plural = _('Posts')
        indexes = (
            BTreeIndex(fields=('token',), condition=Q(post_state__in=[PostState.NEW, PostState.PUBLISHED])),
        )

    phone_number = models.CharField(max_length=11, verbose_name=_('Phone number'), db_index=True)

    token = models.CharField(unique=True, max_length=20, verbose_name=_('Token'))
 
    post_state = models.SmallIntegerField(choices=[
        (PostState.NEW, _('New')),
        (PostState.PUBLISHED, _('Published')),
        (PostState.ARCHIVED, _('Archive')),
        (PostState.REMOVED_BEFORE_PUBLISH, _('Removed before publish')),
        (PostState.REJECTED_AFTER_PUBLISH, _('Rejected after publish')),
    ], default=PostState.NEW, verbose_name=_('Post state'))

我们在模型的 Meta 部分创建索引，它有一个条件参数，您可以在其中传递部分条件。

Answer 2

从 Django indexes and index options 开始，您可以简单地将索引添加到模型元 class:

from django.db.models import Index

class Meta:
        indexes = [
            Index(fields=['phone_number',], condition=Q(post_state__in=[PostState.NEW, PostState.PUBLISHED])),
            Index(fields=['token',], condition=Q(post_state__in=[PostState.NEW, PostState.PUBLISHED])),
            ... # other indexes
        ]

如何在 Django 2.2 模型中创建部分索引

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