在Solr SynonymFilterFactory中使用expand = true？

Question

Solr doc解释了expand = true在SynonymFilterFactory中的作用如下:

a synonym will be expanded to all equivalent synonyms. 
If it is false, all equivalent synonyms will be reduced to the first in the list. 

我想知道它究竟意味着什么？如果有人可以详细说明它的作用,那就太好了.

Answer 1

来自Solr Wiki 上的Solr SynonymFilterFactory文档：

 # If expand==true, "ipod, i-pod, i pod" is equivalent to the explicit mapping:
 ipod, i-pod, i pod => ipod, i-pod, i pod

 # If expand==false, "ipod, i-pod, i pod" is equivalent to the explicit mapping:
 ipod, i-pod, i pod => ipod

由于 Solr SynonymFilterFactory 现已弃用，因此现在使用 SynonymGraphFilterFactory 类。这个答案对于 SynonymGraphFilterFactory 仍然适用。