Tajo JDBC Driver¶

How to get JDBC driver¶

$ tar xzvf tajo-x.y.z-src.tar.gz
$ mvn clean package -DskipTests -Pdist -Dtar
$ ls -l tajo-dist/target/tajo-x.y.z/share/jdbc-dist/tajo-jdbc-x.y.z.jar

Setting the CLASSPATH¶

In order to use the JDBC driver, you should add tajo-jdbc-x.y.z.jar in your CLASSPATH.

CLASSPATH=path/to/tajo-jdbc-x.y.z.jar:$CLASSPATH

Connecting to the Tajo cluster instance¶

A Tajo cluster is represented by a URL. Tajo JDBC driver can take the following URL forms:

• jdbc:tajo://host/
• jdbc:tajo://host/database
• jdbc:tajo://host:port/
• jdbc:tajo://host:port/database

Each part of URL has the following meanings:

• host - The hostname of the TajoMaster. You can put hostname or ip address here.
• port - The port number that server is listening. Default port number is 26002.
• database - The database name. The default database name is default.

To connect, you need to get Connection instance from Java JDBC Driver Manager as follows:

Connection db = DriverManager.getConnection(url);

Connection Parameters¶

Connection parameters lets the JDBC Copnnection to enable or disable additional features. You should use java.util.Properties to pass your connection parameters into Connection. The following example means that the transmission of ResultSet uses compression and its connection timeout is 15 seconds.

String url = "jdbc:tajo://localhost/test";
Properties props = new Properties();
props.setProperty("useCompression","true");  // use compression for ResultSet
props.setProperty("connectTimeout","15000"); // 15 seconds
Connection conn = DriverManager.getConnection(url, props);

The connection parameters that Tajo currently supports are as follows:

• useCompression = bool - Enable compressed transfer for ResultSet.
• defaultRowFetchSize = int - Determine the number of rows fetched in ResultSet by one fetch with trip to the Server.
• connectTimeout = int (seconds) - The timeout value used for socket connect operations. If connecting to the server takes longer than this value, the connection is broken. The timeout is specified in seconds and a value of zero means that it is disabled.
• socketTimeout = int (seconds) - The timeout value used for socket read operations. If reading from the server takes longer than this value, the connection is closed. This can be used as both a brute force global query timeout and a method of detecting network problems. The timeout is specified in seconds and a value of zero means that it is disabled.
• retry = int - Number of retry operation. Tajo JDBC driver is resilient against some network or connection problems. It determines how many times the connection will retry.

An Example JDBC Client¶

The JDBC driver class name is org.apache.tajo.jdbc.TajoDriver. You can get the driver Class.forName("org.apache.tajo.jdbc.TajoDriver"). The connection url should be jdbc:tajo://<TajoMaster hostname>:<TajoMaster client rpc port>/<database name>. The default TajoMaster client rpc port is 26002. If you want to change the listening port, please refer Cluster Setup.

The following shows an example of JDBC Client.

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class TajoJDBCClient {

  ....

  public static void main(String[] args) throws Exception {

    try {
      Class.forName("org.apache.tajo.jdbc.TajoDriver");
    } catch (ClassNotFoundException e) {
      // fill your handling code
    }

    Connection conn = DriverManager.getConnection("jdbc:tajo://127.0.0.1:26002/default");

    Statement stmt = null;
    ResultSet rs = null;
    try {
      stmt = conn.createStatement();
      rs = stmt.executeQuery("select * from table1");
      while (rs.next()) {
        System.out.println(rs.getString(1) + "," + rs.getString(3));
      }
    } finally {
      if (rs != null) rs.close();
      if (stmt != null) stmt.close();
      if (conn != null) conn.close();
    }
  }
}