[LUCENE-8752] Apply a patch to kuromoji dictionary to properly handle Japanese new era '令和' (REIWA)

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 8.1, 9.0
• Component/s: modules/analysis
• Lucene Fields: New, Patch Available
• Assignee: Tomoko Uchida
• Reporter: Tomoko Uchida
• Created: 03/Apr/19 10:20
• Updated: 28/Aug/22 15:43
• Resolved: 13/Apr/19 12:36

Description

As of May 1st, 2019, Japanese era '元号' (Gengo) will be set to '令和' (Reiwa). See this article for more details:

https://www.bbc.com/news/world-asia-47769566

Currently '令和' is splitted up to '令' and '和' by JapaneseTokenizer. It should be tokenized as one word so that Japanese texts including era names are searched as users expect. Because the default Kuromoji dictionary (mecab-ipadic) has not been maintained since 2007, a one-line patch to the source CSV file is needed for this era change.

Era name is used in many official or formal documents in Japan, so it would be desirable the search systems properly handle this without adding a user dictionary or using phrase query.

FYI, JDK DateTime API will support the new era (in the next updates.)

https://blogs.oracle.com/java-platform-group/a-new-japanese-era-for-java

The patch is available here:

https://github.com/apache/lucene-solr/pull/632

 

Issue Links

• links to: GitHub Pull Request #632