ElasticSearch(十七)初识倒排索引

现在有两条document:

doc1:I really liked my small dogs, and I think my mom also liked them.
doc2:He never liked any dogs, so I hope that my mom will not expect me to liked him.

1.分词,初步的倒排索引的建立(*代表有,空代表无):

word        doc1            doc2

I             *            *
really        *
liked         *            *
my            *            *
small         *    
dogs          *
and           *
think         *
mom           *            *
also          *
them          *    
He                         *
never                      *
any                        *
so                         *
hope                       *
that                       *
will                       *
not                        *
expect                     *
me                         *
to                         *
him                        *

 

 

这边演示了一下倒排索引最简单的建立的一个过程  

假设进行搜索:mother like little dog,结果是:不可能有任何结果

过程是将mother like little dog进行一个个拆分,然后进行匹配,无任何匹配信息。

这个是不是我们想要的搜索结果???绝对不是,因为在我们看来,mother和mom有区别吗?同义词,都是妈妈的意思。like和liked有区别吗?没有,都是喜欢的意思,只不过一个是现在时,一个是过去时。little和small有区别吗?同义词,都是小小的。dog和dogs有区别吗?狗,只不过一个是单数,一个是复数。

2.es在建立倒排索引的时候进行了normalization操作

normalization,建立倒排索引的时候,会执行一个操作,也就是说对拆分出的各个单词进行相应的处理,以提升后面搜索的时候能够搜索到相关联的文档的概率。

normalization的意思是进行时态的转换,单复数的转换,同义词的转换,大小写的转换。

mom —> mother
liked —> like
small —> little
dogs —> dog

重新建立倒排索引,加入normalization,再次用mother liked little dog搜索,就可以搜索到了

word        doc1            doc2

I             *            *
really        *
like          *            *            liked --> like
my            *            *
little        *                        small --> little
dog           *            *            dogs --> dog                        
and           *
think         *
mom           *            *
also          *
them          *    
He                         *
never                      * 
any                        *
so                         *
hope                       *
that                       *
will                       *
not                        *
expect                     * 
me                         *
to                         *
him                        *

 

进行搜索:mother like little dog,结果:doc1和doc2都会搜索出来

 

posted @ 2019-05-19 17:41  加肥猫咪  阅读(...)  评论(... 编辑 收藏