This plugin is outdated since elasticsearch 1.1.0 (http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html).
This plugin is outdated since elasticsearch 1.1.0 (http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html).