ICU Analysis for Elasticsearch

The ICU Analysis plugin integrates Lucene ICU module into elasticsearch, adding ICU relates analysis components.

In order to install the plugin, simply run:

bin/plugin -install elasticsearch/elasticsearch-analysis-icu/2.4.1

You need to install a version matching your Elasticsearch version:

elasticsearch	ICU Analysis Plugin	Docs
master	Build from source	See below
es-1.x	Build from source	2.5.0-SNAPSHOT
es-1.4	2.4.1	2.4.1
es-1.3	2.3.0	2.3.0
es-1.2	2.2.0	2.2.0
es-1.1	2.1.0	2.1.0
es-1.0	2.0.0	2.0.0
es-0.90	1.13.0	1.13.0

To build a SNAPSHOT version, you need to build it with Maven:

mvn clean install
plugin --install analysis-icu \
       --url file:target/releases/elasticsearch-analysis-icu-X.X.X-SNAPSHOT.zip

ICU Normalization

Normalizes characters as explained here. It registers itself by default under icu_normalizer or icuNormalizer using the default settings. Allows for the name parameter to be provided which can include the following values: nfc, nfkc, and nfkc_cf. Here is a sample settings:

{
    "index" : {
        "analysis" : {
            "analyzer" : {
                "normalized" : {
                    "tokenizer" : "keyword",
                    "filter" : ["icu_normalizer"]
                }
            }
        }
    }
}

ICU Folding

Folding of unicode characters based on UTR#30. It registers itself under icu_folding and icuFolding names. Sample setting:

{
    "index" : {
        "analysis" : {
            "analyzer" : {
                "folded" : {
                    "tokenizer" : "keyword",
                    "filter" : ["icu_folding"]
                }
            }
        }
    }
}

ICU Filtering

The folding can be filtered by a set of unicode characters with the parameter unicodeSetFilter. This is useful for a non-internationalized search engine where retaining a set of national characters which are primary letters in a specific language is wanted. See syntax for the UnicodeSet here.

The Following example exempts Swedish characters from the folding. Note that the filtered characters are NOT lowercased which is why we add that filter below.

{
    "index" : {
        "analysis" : {
            "analyzer" : {
                "folding" : {
                    "tokenizer" : "standard",
                    "filter" : ["my_icu_folding", "lowercase"]
                }
            }
            "filter" : {
                "my_icu_folding" : {
                    "type" : "icu_folding"
                    "unicodeSetFilter" : "[^åäöÅÄÖ]"
                }
            }
        }
    }
}

ICU Tokenizer

Breaks text into words according to UAX #29: Unicode Text Segmentation.

{
    "index" : {
        "analysis" : {
            "analyzer" : {
                "tokenized" : {
                    "tokenizer" : "icu_tokenizer",
                }
            }
        }
    }
}

ICU Normalization CharFilter

Normalizes characters as explained here. It registers itself by default under icu_normalizer or icuNormalizer using the default settings. Allows for the name parameter to be provided which can include the following values: nfc, nfkc, and nfkc_cf. Allows for the mode parameter to be provided which can include the following values: compose and decompose. Use decompose with nfc or nfkc, to get nfd or nfkd, respectively. Here is a sample settings:

{
    "index" : {
        "analysis" : {
            "analyzer" : {
                "normalized" : {
                    "tokenizer" : "keyword",
                    "char_filter" : ["icu_normalizer"]
                }
            }
        }
    }
}

License

This software is licensed under the Apache 2 license, quoted below.

Copyright 2009-2014 Elasticsearch <http://www.elasticsearch.org>

Licensed under the Apache License, Version 2.0 (the "License"); you may not
use this file except in compliance with the License. You may obtain a copy of
the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations under
the License.