Apache Calcite |使用关系代数从MongoDB查询数据

<dependency>
    <groupId>org.apache.calcite</groupId>
    <artifactId>calcite-core</artifactId>
    <version>VERSION</version>
</dependency>

import org.apache.calcite.adapter.mongodb.MongoSchema;
import org.apache.calcite.config.Lex;
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;

// 创建Calcite连接
Properties info = new Properties();
info.setProperty("lex", Lex.MYSQL.toString());
Connection connection = DriverManager.getConnection("jdbc:calcite:", info);
CalciteConnection calciteConnection = connection.unwrap(CalciteConnection.class);

// 创建MongoDB Schema
SchemaPlus rootSchema = calciteConnection.getRootSchema();
MongoSchema mongoSchema = MongoSchema.create(rootSchema, "mongoSchema", "mongodb://localhost:27017");
rootSchema.add("mongoSchema", mongoSchema);

// 创建查询语句
String query = "SELECT * FROM mongoSchema.collectionName WHERE field = 'value'";

// 执行查询
Statement statement = calciteConnection.createStatement();
ResultSet resultSet = statement.executeQuery(query);

// 处理查询结果
while (resultSet.next()) {
    // 处理每一行的数据
    // 例如，获取字段值：resultSet.getString("fieldName")
}

// 关闭连接和资源
resultSet.close();
statement.close();
connection.close();