Calcite源码阅读二

一、利用calcite项目使用sql读取csv文件
进入calcite的example/csv module，在该module下新建main方法的函数，代码如下

  public static void main(String[] args) throws Exception{
  Properties info = new Properties();
  info.put("model",
      "inline:"
          + "{\n"
          + "  version: '1.0',\n"
          + "  defaultSchema: 'SALES',\n"
          + "   schemas: [\n"
          + "     {\n"
          + "       name: 'SALES',\n"
          + "       tables: [\n"
          + "         {\n"
          + "           name: 'DEPTS',\n"
          + "           type: 'custom',\n"
          + "           factory: 'org.apache.calcite.adapter.csv.CsvTableFactory',\n"
          + "           operand: {\n"
          + "             file: '/Users/xxx/project/calcite/example/csv/src/test/resources/sales/DEPTS.csv',\n"
          + "             flavor: 'scannable'\n"
          + "           }\n"
          + "         }\n"
          + "       ]\n"
          + "     }\n"
          + "   ]\n"
          + "}");
  Connection connection = DriverManager.getConnection("jdbc:calcite:", info);
  Statement statement = connection.createStatement();
  ResultSet rs = statement.executeQuery("select * from DEPTS");
  while (rs.next()) {
    System.out.println(rs.getString(1));
  }
  rs.close();
  statement.close();
  connection.close();
}

其中file是自己本地文件路径，通过这种方式可以使用select方法访问DEPTS.csv文件，执行项目输出

  10
  20
  30

至此，我们完成了calcite项目的基本使用方式