要在Apache Calcite中集成CSV和MySQL,可以使用Calcite的Adapter模块和JDBC接口。下面是一个示例代码:
首先,确保你已经将Apache Calcite和相关的依赖项添加到你的项目中。
接下来,创建一个CSV的模型文件,用于描述CSV数据源的结构和位置。假设CSV文件的路径为"/path/to/csv/file.csv",并且包含两个列:id和name。创建一个名为"csvModel.json"的文件,并将以下内容保存到该文件中:
{
"version": "1.0",
"defaultSchema": "csv",
"schemas": [
{
"name": "csv",
"type": "custom",
"factory": "org.apache.calcite.adapter.csv.CsvSchemaFactory",
"operand": {
"directory": "/path/to/csv",
"tables": [
{
"name": "table1",
"factory": "org.apache.calcite.adapter.csv.CsvTableFactory",
"operand": {
"file": "file.csv",
"flavor": "scannable"
}
}
]
}
}
]
}
然后,创建一个MySQL的模型文件,用于描述MySQL数据源的连接信息和结构。创建一个名为"mysqlModel.json"的文件,并将以下内容保存到该文件中:
{
"version": "1.0",
"defaultSchema": "mysql",
"schemas": [
{
"name": "mysql",
"type": "jdbc",
"factory": "org.apache.calcite.adapter.jdbc.JdbcSchema$Factory",
"operand": {
"jdbcUrl": "jdbc:mysql://localhost:3306/mydatabase",
"jdbcDriver": "com.mysql.jdbc.Driver",
"jdbcUser": "username",
"jdbcPassword": "password"
}
}
]
}
接下来,使用以下代码加载CSV和MySQL模型,并进行查询操作:
import org.apache.calcite.jdbc.CalciteConnection;
import org.apache.calcite.schema.SchemaPlus;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;
public class CalciteExample {
public static void main(String[] args) throws Exception {
// Load the CSV model
Properties csvProps = new Properties();
csvProps.setProperty("model", "csvModel.json");
Connection csvConn =
DriverManager.getConnection("jdbc:calcite:", csvProps);
CalciteConnection csvCalciteConn = csvConn.unwrap(CalciteConnection.class);
SchemaPlus csvSchema = csvCalciteConn.getRootSchema().getSubSchema("csv");
// Load the MySQL model
Properties mysqlProps = new Properties();
mysqlProps.setProperty("model", "mysqlModel.json");
Connection mysqlConn =
DriverManager.getConnection("jdbc:calcite:", mysqlProps);
CalciteConnection mysqlCalciteConn = mysqlConn.unwrap(CalciteConnection.class);
SchemaPlus mysqlSchema = mysqlCalciteConn.getRootSchema().getSubSchema("mysql");
// Set up the query
Statement stmt = mysqlConn.createStatement();
String query = "SELECT t1.id, t1.name FROM mysql.table1 AS t1 " +
"JOIN csv.table1 AS t2 ON t1.id = t2.id";
// Execute the query
ResultSet rs = stmt.executeQuery(query);
// Process the result
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
System.out.println("id: " + id + ", name: " + name);
}
// Clean up
rs.close();
stmt.close();
mysqlConn.close();
csvConn.close();
}
}
请确保将上述代码中的"/path/to/csv/file.csv"替换为你实际的CSV文件路径,"jdbc:mysql://localhost:3306/mydatabase"替换为你实际的MySQL数据库连接信息,以及"username"和"password"替换为你实际的MySQL用户名和密码。
这是一个基本的示例,你可以根据自己的需求进行修改和扩展。