Dynamic mapping templates have been defined for various field usage. Select the correct mapping for your field by prepending the specified prefix.
Example: a field named text_message will by mapped as an analyzed string field, a field named ni_request_tag will not be indexed.
The default mapping template for string fields is keyword.
In many cases you might want to modify the prefixes to match the current naming scheme in your code. e.g. I frequently change ID_* to *Id to accomodate field names like requestId. In typed languages like Java/Scala you could have the serializer emit fields with appropriate prefixes for you.