Lowercase token filter
editLowercase token filter
editChanges token text to lowercase. For example, you can use the lowercase filter
to change THE Lazy DoG to the lazy dog.
In addition to a default filter, the lowercase token filter provides access to
Lucene’s language-specific lowercase filters for Greek, Irish, and Turkish.
Example
editThe following analyze API request uses the default
lowercase filter to change the THE Quick FoX JUMPs to lowercase:
GET _analyze
{
"tokenizer" : "standard",
"filter" : ["lowercase"],
"text" : "THE Quick FoX JUMPs"
}
The filter produces the following tokens:
[ the, quick, fox, jumps ]
Add to an analyzer
editThe following create index API request uses the
lowercase filter to configure a new
custom analyzer.
PUT lowercase_example
{
"settings" : {
"analysis" : {
"analyzer" : {
"whitespace_lowercase" : {
"tokenizer" : "whitespace",
"filter" : ["lowercase"]
}
}
}
}
}
Configurable parameters
edit-
language -
(Optional, string) Language-specific lowercase token filter to use. Valid values include:
-
greek - Uses Lucene’s GreekLowerCaseFilter
-
irish - Uses Lucene’s IrishLowerCaseFilter
-
turkish - Uses Lucene’s TurkishLowerCaseFilter
If not specified, defaults to Lucene’s LowerCaseFilter.
-
Customize
editTo customize the lowercase filter, duplicate it to create the basis
for a new custom token filter. You can modify the filter using its configurable
parameters.
For example, the following request creates a custom lowercase filter for the
Greek language:
PUT custom_lowercase_example
{
"settings": {
"analysis": {
"analyzer": {
"greek_lowercase_example": {
"type": "custom",
"tokenizer": "standard",
"filter": ["greek_lowercase"]
}
},
"filter": {
"greek_lowercase": {
"type": "lowercase",
"language": "greek"
}
}
}
}
}