CJK bigram token filter
editCJK bigram token filter
editForms bigrams out of CJK (Chinese, Japanese, and Korean) tokens.
This filter is included in Elasticsearch’s built-in CJK language analyzer. It uses Lucene’s CJKBigramFilter.
Example
editThe following analyze API request demonstrates how the CJK bigram token filter works.
GET /_analyze
{
"tokenizer" : "standard",
"filter" : ["cjk_bigram"],
"text" : "東京都は、日本の首都であり"
}
The filter produces the following tokens:
[ 東京, 京都, 都は, 日本, 本の, の首, 首都, 都で, であ, あり ]
Add to an analyzer
editThe following create index API request uses the CJK bigram token filter to configure a new custom analyzer.
PUT /cjk_bigram_example
{
"settings" : {
"analysis" : {
"analyzer" : {
"standard_cjk_bigram" : {
"tokenizer" : "standard",
"filter" : ["cjk_bigram"]
}
}
}
}
}
Configurable parameters
edit-
ignored_scripts -
(Optional, array of character scripts) Array of character scripts for which to disable bigrams. Possible values:
-
han -
hangul -
hiragana -
katakana
All non-CJK input is passed through unmodified.
-
output_unigrams
(Optional, boolean)
If true, emit tokens in both bigram and
unigram form. If false, a CJK character
is output in unigram form when it has no adjacent characters. Defaults to
false.
Customize
editTo customize the CJK bigram token filter, duplicate it to create the basis for a new custom token filter. You can modify the filter using its configurable parameters.
PUT /cjk_bigram_example
{
"settings" : {
"analysis" : {
"analyzer" : {
"han_bigrams" : {
"tokenizer" : "standard",
"filter" : ["han_bigrams_filter"]
}
},
"filter" : {
"han_bigrams_filter" : {
"type" : "cjk_bigram",
"ignored_scripts": [
"hangul",
"hiragana",
"katakana"
],
"output_unigrams" : true
}
}
}
}
}