Numeric and boolean fields have doc values enabled by default as of
elasticsearch 2.0. This commit removes support for uninverted/in-memory
fielddata, as well as numeric fields encoded in binary doc values which was
the way that elasticsearch stored doc values in a Lucene index before the
1.4 release.
As a consequence, you will only be able to sort and aggregate on numeric and
boolean fields in Elasticsearch 3.0 if doc values have not been switched off.