通过迁移为Django中的模型字段添加索引 [英] Adding indexes to model fields in Django with migrations

问题描述

我正在尝试使用 Field.db_index 为具有迁移的应用程序添加索引。查看 Django的文档所有我需要做的是设置 db_index = True ：

I am trying to add indexes on model fields using Field.db_index for an app that has migrations. Looking at Django's documentation all I need to do is to set db_index=True:

class Person(models.Model):
    first_name = models.CharField()
    last_name = models.CharField(db_index=True)

然后我第一次尝试新的Django的迁移：

and then I first tried the new Django's Migration:

./manage.py makemigrations app-name

但是Migration似乎没有注意到这个更改，并且没有添加sql命令创建索引。所以我试过 django-admin.py 如这里：

but Migration does not seem to notice the change and does not add the sql command for creating an index. So I tried django-admin.py as explained here:

django-admin.py sqlindexes app-name

但是，不会打印sql命令，并退出并显示以下错误：

But that does not print the sql command either and it exits with the following error:

CommandError: App 'app-name' has migrations. Only the sqlmigrate and sqlflush commands can be used when an app has migrations.

推荐答案

好的，我设法使用 Meta.index_together 。这不是最干净的方法，因为我实际上并不是将多个字段编入索引，而是与 makemigrations 一起使用：

OK, I managed to create the indexes using Meta.index_together. It is not the cleanest way, since I am not actually indexing multiple fields together but it works with makemigrations:

class Person(models.Model):
    class Meta():
        index_together = [['last_name']]
    first_name = models.CharField()
    last_name = models.CharField()

现在 makemigrations 确实进行了新的迁移：

Now makemigrations does make a new migration:

./manage.py makemigrations app-name

>>Migrations for 'app-name':
>>  0005_auto_20140929_1540.py:
>>    - Alter index_together for Person (1 constraint(s))

相应的sql命令实际上是 CREATE INDEX 。

And the corresponding sql command is actually CREATE INDEX.

./manage.py sqlmigrate app-name 0005_auto_20140929_1540

>>BEGIN;
>>CREATE INDEX app-name_person_last_name_7...4_idx ON `app-name_person` (`last_name`);
>>COMMIT;

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