format_definitions.md

The fields.definitions parameter looks like:

{
    "field_name": {
        "standard": "field_name",
        "precise": "field_name.precise",
        "reverse_precise": "field_name.reverse_precise",
        "prefix_precise": "field_name.prefix"
    }
}

Where field_name is the name of the field you are defining.

All fields in the object under field_name are optional. They default to the format above but they are only used if the fields are actually defined in the mapping. That means that if you define a field that "looks like" the precise field or looks like the reverse_precise field it'll automatically be where appropriate.

You can also add an ngram to configure regular expression support. Note that regular expressions still have to be turned on by configuring a regex settings object. Just configuring a field without that will do nothing. Here is an example for a field rigged for regular expression matching:

{
    "title": {
        "ngram": {
            "name": "title.trigram",
            "gram_size": 3
        }
    }
}

name is required. gram_size defaults to 3.