> For the complete documentation index, see [llms.txt](https://wtifs.gitbook.io/diva-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wtifs.gitbook.io/diva-notes/db/dao-pai-suo-yin.md).

# 倒排索引

倒排索引（Inverted Index）是一种常用的文本索引技术，常用于搜索引擎中。它将文档中的每个词语的出现位置进行记录，并按照词语建立索引，将词语指向文档，从而方便快速地查询包含该词语的文档。倒排索引的名称来源于索引中单词与文档的位置关系被“倒过来”了。

举个例子，有123三个文档，其中1、3文档中包含 "alice bob" 两个词，那么就可以为此生成两个倒排索引，一个 `key` 是 alice，另一个 `key` 是 bob ，`value` 都是 1、3

如果用户输入查询单词 "alice"，只需要查询倒排索引中包含 "alice" 的文档编号，就可以很快地找到相关文档。倒排索引可以大大提高文本检索的效率和准确性。

再举个例子，有123三个用户，用户1是北京的，用户2也是北京的，用户3是深圳的，就可以建立 "北京" 和 "深圳" 两个倒排索引


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