Hightlight on all fields


I'm new to elastic search and am wondering if there is a way to highlight on all fields.

Looks like highlighting requires me to explicitly specify the field names.
My understanding is that if I want to highlight on all fields, I will have to use _all but that requires me to store the _all field that will increase index size and requires some mapping for _all.

Is there any way to highlight on all fields without having to store extra data or mapping?

Any sample query will be appreciated.