isFirst() returns true when relative(x) goes beyond result set

• Key: DERBY-186
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: Unassigned
• Reporter: George Baklarz
• Component/s: JDBC
• Affects Version/s: 10.0.2.0
• Fix Version/s: 10.1.1.0

Description

Bizarre error. Not sure if this is a JDBC, Derby, or Java issue.

An opened result set has 4 records. A call to relative(3) while on row 3 should result in isAfterLast=true, and isFirst, isBeforeFirst, and IsLast set to false. However, the result is isAfterLast=True and isFirst=True.

ij
connect 'IsAfter;create=true';
create table x (a char(1));
insert into x values '1','2','3','4';
quit;

import java.sql.*;

public class ErrIsFirst {

  public static void main(String argv[]) throws SQLException {

    Connection conn = null;
    Statement s = null;
    ResultSet rs = null;
    String DerbyDriver = "org.apache.derby.jdbc.EmbeddedDriver";
    String returnValue;
      
    try {
       Class.forName(DerbyDriver).newInstance();
    }
    catch (Exception NoDriver) {
       System.out.println("Derby driver not found: " + DerbyDriver);
       NoDriver.printStackTrace();
       System.exit(1);
    }

    try {
      conn = DriverManager.getConnection("jdbc:derby:IsAfter");
      s = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
      rs = s.executeQuery( "SELECT A FROM X");

      rs.next(); // First Record
      returnValue = rs.getString("A");
      System.out.println("Value="+returnValue);
      
      rs.relative(2);
      System.out.println("isFirst=" + rs.isFirst() + " isLast=" + rs.isLast() + " isAfterLast=" + rs.isAfterLast());
      returnValue = rs.getString("A");
      System.out.println("Value="+returnValue);

      rs.relative(-2);
      returnValue = rs.getString("A");
      System.out.println("Value="+returnValue);
      rs.relative(10);
      System.out.println("isFirst=" + rs.isFirst() + " isLast=" + rs.isLast() + " isAfterLast=" + rs.isAfterLast());
      returnValue = rs.getString("A");
      System.out.println("Value="+returnValue);
      rs.close();
      s.close();
    }
    catch (SQLException se) {
      String SQLState = se.getSQLState();
      String SQLMessage = se.getMessage();
      System.out.println("Error = "+SQLState);
      System.out.println(SQLMessage);
    }
  }
}

The results on my system are:
Value=1
isFirst=false isLast=false isAfterLast=false
Value=3
Value=1
isFirst=true isLast=false isAfterLast=true
Error = 24000
Invalid cursor state - no current row.

If you eliminate the first println call to isFirst() you get the following (correct) results.

Value=1
Value=3
Value=1
isFirst=false isLast=false isAfterLast=true
Error = 24000
Invalid cursor state - no current row.

Okay, so where did we go wrong?

Comments

[Shreyas Kaushik]

I guess the problem is not whether you make a call to isFirst() first or next. The way a call to relative() is behaving when the param passed to it is more than the number of rows, is what is causing the problem.

I have small fix going for this which I am still testing. Will update when I get some results.

~ Shreyas

Fix provided by Shreyas and committed to trunk version.

[Satheesh Bandaram]

Fix checked in.