Django模型字段索引 [英] Django Model Fields Indexing

问题描述

我只知道索引是有用的，而且查询速度更快。

I only know that indexing is helpful and it queries faster.

后面的两个有什么区别？

What is the difference between following two?

1. class Meta:
       indexes = [
           models.Index(fields=['last_name', 'first_name',]),
           models.Index(fields=['-date_of_birth',]),
]

2. class Meta:
       indexes = [
            models.Index(fields=['first_name',]),
            models.Index(fields=['last_name',]),
            models.Index(fields=['-date_of_birth',]),
]

推荐答案

示例1：

第一个示例在 last_name 和 first_name 字段上创建一个索引。

The first example creates a single index on the last_name and first_name field.

indexes = [
   models.Index(fields=['last_name', 'first_name',]),
]

如果您一起搜索姓氏和名字，或者单独搜索姓氏，这将很有用（因为 last_name 是索引中的第一个字段）。

It will be useful if you search on the last name and first name together, or the last name by itself (because last_name is the first field in the index).

MyModel.objects.filter(last_name=last_name, first_name=first_name)
MyModel.objects.filter(last_name=last_name)

但是，对于搜索 first_name 本身（因为 first_name 不是索引中的第一个字段）。

However, it will not be useful for searching for the first_name by itself (because first_name is not the first field in the index).

MyModel.objects.filter(first_name=first_name)  # not useful

示例2：

第二个示例为 first_name 字段和 last_name 字段的单独索引。

The second example creates an index for the first_name field and a separate index for the last_name field.

indexes = [
    models.Index(fields=['first_name',]),
    models.Index(fields=['last_name',]),
]

如果您根据代码中的名字或姓氏进行查找，则很有用

It will be useful if you do lookups based on first name or last name in your code

MyModel.objects.filter(first_name=search)
MyModel.objects.filter(last_name=search)

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