參考：
es-sql: https://github.com/NLPchina/elasticsearch-sql/releases
執行SQL語句
SearchDao org.nlpcn.es4sql.SearchDao.SearchDao
searchDao.explain(sqlStr).explain().get();
索引列表: http://teknosrc.com/elasticsearch-java-api-get-index-list/
索引類型列表： http://teknosrc.com/elasticsearch-java-api-get-index-type-list-mapping/
類型字段列表： http://teknosrc.com/elasticsearch-java-api-get-field-list-given-index-ype/