Noticed this option in 2.1 document and it is saying doc_values supposed to be more efficient for sorting and aggregating. However we are running 1.7 in production and wanna check if such mapping is available in ES 1.7 and how the efficiency is compared with fielddata.
For the most part, doc_values is available in 1.7 as well. (There are a few exceptions like _type didn't use doc_values until 2.1, for example, but most of it's there in 1.7).
Chris wrote a really great blog at https://www.elastic.co/blog/support-in-the-wild-my-biggest-elasticsearch-problem-at-scale comparing doc_values vs fielddata and why we really think doc_values is the best way forward. It does mean you should make sure you leave enough RAM for your OS's filesystem cache, since your OS should cache the doc_values in memory.