Lowercase token filter

Changes 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

The 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

The 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

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

To 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" } } } } }  