https://groups.google.com/d/topic/elasticsearch/L5RVcreJSbs/discussion

script_field_facet.sh

curl -XDELETE localhost:9200/test-idx
curl -XPUT localhost:9200/test-idx -d '{
    "settings": {
        "index.number_of_shards": 1,
        "index.number_of_replicas": 0
    },
    "mappings": {
        "doc": {
            "properties": {
                "foo": {"type": "string", "index": "not_analyzed"},
                "bar": {"type": "string", "index": "not_analyzed"}
            }
        }
    }
}'
curl -XPOST localhost:9200/test-idx/doc -d '{"foo": "1", "bar": "A"}'
curl -XPOST localhost:9200/test-idx/doc -d '{"foo": "2", "bar": "A"}'
curl -XPOST localhost:9200/test-idx/doc -d '{"foo": "1", "bar": "B"}'
curl -XPOST localhost:9200/test-idx/doc -d '{"foo": "2", "bar": "B"}'
curl -XPOST localhost:9200/_refresh
echo
curl "localhost:9200/test-idx/doc/_search?pretty=true&search_type=count" -d '{
    "facets": {
        "test": {
            "terms": {
                "script": {
                    "script_field" : "doc[\"foo\"].value+\"-\"+doc[\"bar\"].value"
                }
            }
        }
    }
}'