大家讨论的时候，提供了两个选择，一个是apache calcite, 另外一个是利用 alibaba 的jdbc 连接池 druid。最后我选择了使用druid 来完成。为啥不用第一个的原因如下：
I have tried calcite to add this feature to es-sql. It's proved to be unsuitable. calcite kind like spark datasource API which provide scanTable,filterTabe,translateTable which means you cannot access original sql(Raw SQL) but some expressions . Also, this means join ,group by action are all done in calcite which really impact performance .
PS: 该功能还只是Demo阶段，很多功能还不完备。等稳定后会合并到原项目中。目前经过几轮PR,
elasticsearch-sql 已经支持比较复杂的SQL语法了。
安装步骤
代码示例
public class JDBCTests {
@Test
public void testJDBC() throws Exception {
Properties properties = new Properties();
properties.put("url", "jdbc:elasticsearch://127.0.0.1:9300/twitter2");
DruidDataSource dds = (DruidDataSource) ElasticSearchDruidDataSourceFactory.createDataSource(properties);
dds.setInitialSize(1);
Connection connection = dds.getConnection();
PreparedStatement ps = connection.prepareStatement("SELECT split(trim(concat_ws('dd',newtype,num_d)),'dd')[0] as nt from twitter2");
ResultSet resultSet = ps.executeQuery();
while (resultSet.next()) {
System.out.println(resultSet.getString("nt"));
}
ps.close();
connection.close();
dds.close();
}
}
