Right now doc values are enabled on a field if its fielddata format is doc_values at creation time of the field mapper.

So if you create a field with the doc_values fielddata format, then use the update mapping API to change the format to paged_bytes instead and restart the node, the field mapper won't know that it needs to index doc values and the doc_values format won't be usable anymore.

I'd like to have a doc_values setting on the same level as index and store in the mappings that would remain true even when the field data format becomes paged_bytes so that doc values keep being indexed and the fielddata format can be later set to doc_values again.