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The ICU analysis
plug-in for Elasticsearch uses the International Components for Unicode
(ICU) libraries (see site.project.org) to
provide a rich set of tools for dealing with Unicode.
These include the
icu_tokenizer, which is particularly useful for Asian languages,
and a number
of token filters that are essential for correct matching and sorting in all
languages other than English.
The ICU plug-in is an essential tool for dealing with languages other than English, and it is highly recommended that you install and use it. Unfortunately, because it is based on the external ICU libraries, different versions of the ICU plug-in may not be compatible with previous versions. When upgrading, you may need to reindex your data.
To install the plug-in, first shut down your Elasticsearch node and then run the following command from the Elasticsearch home directory:
Once installed, restart Elasticsearch, and you should see a line similar to the following in the startup logs:
[INFO][plugins] [Mysterio] loaded [marvel, analysis-icu], sites [marvel]
If you are running a cluster with multiple nodes, you will need to install the plug-in on every node in the cluster.