Why xwiki do not search the 'title_" field in Solr?

Why xwiki do not search the 'title_" field in Solr?

I use debug=true on search, found that, XWiki DO NOT search the tilte_ field, but “tilte__” (double underline) instead. But “title_” is the field which SOLR indexed.
Even with “tilte__”, it split my Chinese word into individual chars. It prevents SOLR search engine to get good result.

Search: title:搜索中台

Debug Information

Query Parser

  • ExtendedDismaxQParser

Parsed Query

  • +((title_en:搜 title_en:索 title_en:中 title_en:台) | (title__:搜 title__:索 title__:中 title__:台) | title_zh_CN:搜索中台 | title_zh:搜索中台)

Filter Queries

  • {!tag=hidden}hidden:(false)
  • {!tag=type}type:(“DOCUMENT”)
  • {!tag=locale}locale:(“zh_CN” OR “”)

The document of “搜索中台” in Solr Admin:

{
“id”:“xwiki:SearchDev.SearchMiddleEnd.WebHome_zh”,
“hidden”:false,
“wiki”:“xwiki”,
“name”:“WebHome”,
“space”:“SearchDev.SearchMiddleEnd”,
“spaces”:[“SearchDev”, “SearchMiddleEnd”],
“locale”:“zh”,
“language”:“zh”,
“type”:“DOCUMENT”,
“fullname”:“SearchDev.SearchMiddleEnd.WebHome”,
“title_”:“搜索中台”,
“doccontentraw_”:"……",
“doccontent_”:"……",
“version”:“35.1”,
“doclocale”:"",
“locales”:["", “zh_CN”, “zh”,“en”],
“lang”:["", “zh_CN”, “zh”, “en”],
“author”:“xwiki:XWiki.kirbyzhou”,
“author_display”:"-",
“creator”:“xwiki:XWiki.kirbyzhou”,
“creator_display”:"-",
“creationdate”:“2019-05-23T08:42:35Z”,
“date”:“2020-02-22T06:57:05Z”,
version ”:1659219083949768704,
“score”:15.423278}

See https://jira.xwiki.org/browse/XWIKI-14091 .