5.3.1 In That Case
The most frequently used token filter is the lowercase
filter, which does exactly what you would expect; it transforms each token into its lowercase form:
GET /_analyze?tokenizer=standard&filters=lowercase
The QUICK Brown FOX! ①
① Emits tokens the
, quick
, brown
, fox
It doesn’t matter whether users search for fox
or FOX
, as long as the same analysis process is applied at query time and at search time. The lowercase
filter will transform a query for FOX
into a query for fox
, which is the same token that we have stored in our inverted index.
To use token filters as part of the analysis process, we can create a custom
analyzer:
PUT /my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_lowercaser": {
"tokenizer": "standard",
"filter": [ "lowercase" ]
}
}
}
}
}
And we can test it out with the analyze
API:
GET /my_index/_analyze?analyzer=my_lowercaser
The QUICK Brown FOX! ①
① Emits tokens the, quick, brown, fox