Java DatabaseMetaData getMaxIndexLength Method with Example

The getMaxIndexLength() method of the DatabaseMetaData interface is used to find out the maximum number of bytes that the underlying database allows for an index.

This method returns an integer value, representing the maximum number of byes allowed in an index. If this value is 0 it indicates that there is no limit or, limit is unknown.

To get the DatabaseMetaData object −

• Make sure your database is up and running.

• Register the driver using the registerDriver() method of the DriverManager class. Pass an object of the driver class corresponding to the underlying database.

• Get the connection object using the getConnection() method of the DriverManager class. Pass the URL the database and, user name, password of a user in the database, as String variables.

• Get the DatabaseMetaData object with respect to the current connection using the getMetaData() method of the Connection interface.

Finally, get the maximum number of bytes allowed in index, by invoking the getMaxIndexLength() method (of the DatabaseMetaData interface).

Example

Following JDBC example connects to MySQL database, retrieves and prints the maximum length of the index allowed, by it.

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DatabaseMetadata_getMaxIndexLength {
   public static void main(String args[]) throws SQLException {
      //Registering the Driver
      DriverManager.registerDriver(new com.mysql.jdbc.Driver());
      //Getting the connection
      String url = "jdbc:mysql://localhost/mydatabase";
      Connection con = DriverManager.getConnection(url, "root", "password");
      System.out.println("Connection established......");
      //Retrieving the meta data object
      DatabaseMetaData metaData = con.getMetaData();
      //Retrieving the maximum length(size) of the index supported
      int maxLength = metaData.getMaxIndexLength();
      System.out.println("Maximum length(size) of the index supported: "+maxLength);
   }
}

Output

Connection established......
Maximum length(size) of the index supported: 256