executeQuery 不返回 Hive 的结果

Question

我正在尝试将数据从 Hive 导出到 Teradata。下面是我的代码：

/* Code Start */
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class HiveToTd {
private final static String tdUser = "**********";
private final static String tdPass = "**********";

private final static String hiveUser = "**********";
private final static String hivePass = "**********";

private static String driverName = "org.apache.hive.jdbc.HiveDriver";
/**
 * @param args
 * @throws ClassNotFoundException 
 * @throws SQLException 
 */
public static void main(String[] args) throws ClassNotFoundException, SQLException {
    // Get the Teradata connection 
    Class.forName("com.teradata.jdbc.TeraDriver");
    Connection tdcon = DriverManager.getConnection("jdbc:teradata://database.XXXXX.com/TMODE=ANSI,TYPE=FASTLOAD", tdUser, tdPass);
    System.out.println("Connected to Teradata.");
    
    // Get our hive connection
    Class.forName(driverName);
    System.out.println("Connecting to Hive.");
    Connection hivecon = DriverManager.getConnection("jdbc:hive2://bigdatabase.xxxxxx.com:10000/default", hiveUser, hivePass);
    System.out.println("Connected to Hive.");
    
    // Select our table from Hive
    
    Statement hst = hivecon.createStatement();
    System.out.println("Executing Statement");
    ResultSet hrs = hst.executeQuery("SELECT COL1, COL2, COL3 FROM db.table limit 100");
    
    System.out.println("Get DATA");
    int count= 0;
    if(hrs.next())
    {
        count++;
    }
  System.out.println(count);

计数返回“1”而不是 100。我已验证我在 Hive 的表中有超过 100 万条记录。我究竟做错了什么？它只是返回标题行，仅此而已。我本以为问题出在连接上，但它给了我正确的标题行。所以它必须是别的东西。

更新

所以看起来代码确实有效。感谢您帮助我解决 Thusitha 问题。

下一段比较麻烦。这是为了快速加载到 TD。

// Empty the staging table
    tdcon.createStatement().executeUpdate("delete from dbname.staging_table");

    // Create prepared statement for Teradata
    System.out.println("Begin load to Teradata");
    tdcon.setAutoCommit(false);
    
    PreparedStatement ps = tdcon.prepareStatement("insert into dbname.staging_table values (?,?,?)");
    System.out.println("Start Fastload");
    int i;
    for (i = 1; hrs.next(); i++){
        ps.setString(1, hrs.getString(1));
        ps.setString(2, hrs.getString(2));
        ps.setString(3, hrs.getString(3));
        ps.addBatch();
        System.out.println(i);
        if (i % 10000 == 0){
            ps.executeBatch();
        }
    }
    
    
    
    if (i % 10000 != 0){
        ps.executeBatch();
    }
    
    
    
    tdcon.commit();
    tdcon.setAutoCommit(true);
    ps.close();
    hrs.close();
    
    sideLoad("dbname.staging_table", "dbname.final_table", tdcon);
    tdcon.close();
    hivecon.close();
    
}

public static int sideLoad(String fromTable, String toTable, Connection conn) throws SQLException{
    return (conn.createStatement().executeUpdate("INSERT INTO " + toTable + " SELECT * FROM " + fromTable));
    
}



}

“启动快速加载”消息后我得到的错误是：

Exception in thread "main" java.sql.SQLException: [Teradata JDBC Driver] [TeraJDBC 15.00.00.20] [Error 1103] [SQLState HY000] Cannot add an empty batch of rows to a database table
    at com.teradata.jdbc.jdbc_4.util.ErrorFactory.makeDriverJDBCException(ErrorFactory.java:94)
    at com.teradata.jdbc.jdbc_4.util.ErrorFactory.makeDriverJDBCException(ErrorFactory.java:64)
    at com.teradata.jdbc.jdbc.fastload.FastLoadManagerPreparedStatement.executeBatch(FastLoadManagerPreparedStatement.java:2049)
    at com.optus.insights.HiveToTd.main(HiveToTd.java:84)

Answer 1

你有一个

if

条件 所以计数它只会转到 ResultSet 的第一行并递增计数 1

如果要遍历所有行，请使用

while loop

而不是

if

更改您的代码如下

while(hrs.next()){
    count++;
}