See the Elasticsearch documentation: multi-fields
See also HSEARCH-2215
The idea is to define additional fields that take the same input as other fields, but transform/store it differently.
We could use a "source" or "derivedFrom" or "subFieldOf" attribute on @XXXField annotation:
Note that we would have to forbid the definition of a bridge on such field, because the copy happens automatically in the backend.
The backend APIs could expose something like this:
Or maybe a better API could be designed while we address HSEARCH-3444 .