Fields with doc_values=true populate fielddata cache

I have an index with single mapping and almost all fields with doc_values=true. Fisrt time after adding doc_values filddata contains only boolean fields. But now stats shows that all those fields present in fielddata cache. Not only string and boolean fields but numeric too.

And I have the frustration of how this could happen.

Elasticsearch version: 1.7.1


I'm sorry, system administrator gave me mapping from another cluster. So all is ok.