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Date: Wed, 08 Jun 2005 23:32:29 +0200
From: "Bernt M. Johnsen" <Bernt.Johnsen@Sun.COM>
Subject: Re: [PATCH] (DERBY-276) ResultSet.relative(int row) cannot be called
 when the cursor is not positioned on a row.
In-reply-to: <20050527123139.GA30208@atum01.norway.sun.com>
To: derby-dev@db.apache.org
Message-id: <20050608213229.GA6409@barbar.sun.com>
Organization: Sun Microsystems
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References: <20050527123139.GA30208@atum01.norway.sun.com>

>>>>>>>>>>>> Bernt M. Johnsen wrote (2005-05-27 14:31:39):
> Could anybody review this?

Well?

> This patch will make relative() allowed when the cursor is before
> first or after last. It will also let absolute(0) be equivalent to
> beforeFirst().
> 
> This should be in accordance with JDBC 3.0 (although the tutorial and
> javadoc as a bit inconsistent on relative()).
> 
> The patch will also cause the Network clinet to deviate from the
> behaviour of DB2JCC.
> 
> derbyall is run with one fail which should not be related to this patch:
> derbyall/derbynetclientmats/derbynetmats.fail:lang/updatableResultSet.java
> 
> derbyall run on:
> Java Version:    1.5.0_03
> Java Vendor:     Sun Microsystems Inc.
> OS name:         Linux
> OS architecture: i386
> OS version:      2.4.20-31.9
> 
> Attached are the patch and the stat.
> -- 
> Bernt Marius Johnsen, Database Technology Group, 
> Sun Microsystems, Trondheim, Norway

> Index: java/tools/org/apache/derby/impl/tools/ij/utilMain.java
> ===================================================================
> --- java/tools/org/apache/derby/impl/tools/ij/utilMain.java	(revision 178761)
> +++ java/tools/org/apache/derby/impl/tools/ij/utilMain.java	(working copy)
> @@ -693,12 +693,7 @@
>  			throw ijException.forwardOnlyCursor("ABSOLUTE");
>  		}
>  
> -		// 0 is an invalid value for row
> -		if (row == 0)
> -		{
> -			throw ijException.zeroInvalidForAbsolute();
> -		}
> -
> +		// 0 is an *VALID* value for row
>  		return new ijRowResult(rs, rs.absolute(row));
>  	}
>  
> Index: java/engine/org/apache/derby/impl/sql/execute/ScrollInsensitiveResultSet.java
> ===================================================================
> --- java/engine/org/apache/derby/impl/sql/execute/ScrollInsensitiveResultSet.java	(revision 178761)
> +++ java/engine/org/apache/derby/impl/sql/execute/ScrollInsensitiveResultSet.java	(working copy)
> @@ -232,10 +232,11 @@
>  			}
>  		}
>  
> -		// 0 is an invalid parameter
> +                // Absolute 0 is defined to be before first!
>  		if (row == 0)
>  		{
> -			throw StandardException.newException(SQLState.LANG_ZERO_INVALID_FOR_R_S_ABSOLUTE);
> +                    setBeforeFirstRow();
> +                    return null;
>  		}
>  
>  		if (row > 0)
> @@ -330,16 +331,14 @@
>  			}
>  		}
>  
> -		/* Throw exception if before first or after last */
> -		if (beforeFirst || afterLast)
> -		{
> -			throw StandardException.newException(SQLState.LANG_NO_CURRENT_ROW_FOR_RELATIVE);
> -		}
> -
>  		// Return the current row for 0
>  		if (row == 0)
>  		{
> +                    if (beforeFirst || afterLast) {
> +                        return null;
> +                    } else {
>  			return getRowFromHashTable(currentPosition);
> +                    }
>  		}
>  		else if (row > 0)
>  		{
> Index: java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors2.java
> ===================================================================
> --- java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors2.java	(revision 178761)
> +++ java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors2.java	(working copy)
> @@ -613,6 +613,16 @@
>  			System.out.println("expected to be before the 1st row");
>  			passed = false;
>  		}
> +                if (rs.absolute(0))
> +                {
> +			System.out.println("absolute(0) expected to return false");
> +			passed = false;
> +                }
> +		if (! rs.isBeforeFirst())
> +		{
> +			System.out.println("still expected to be before the 1st row");
> +			passed = false;
> +		}
>  		// go to first row
>  		if (! rs.first())
>  		{
> @@ -1002,19 +1012,6 @@
>  			passed = passed && checkException(sqle, "XJ062");
>  		}
>  
> -		// absolute(0)
> -		try
> -		{
> -			rs.absolute(0);
> -			System.out.println("absolute(0) expected to fail");
> -			passed = false;
> -		}
> -		catch (SQLException sqle)
> -		{
> -			/* Check to be sure the exception is the one we expect */
> -			passed = passed && checkException(sqle, "X0X86");
> -		}
> -
>  		s_i_r.close();
>  
>  		return passed;
> Index: java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors1.sql
> ===================================================================
> --- java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors1.sql	(revision 178761)
> +++ java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors1.sql	(working copy)
> @@ -25,19 +25,15 @@
>  close c1;
>  
>  get scroll insensitive cursor c1 as 'select * from t1';
> --- 0 is invalid value for absolute
>  absolute 0 c1;
>  close c1;
>  get scroll insensitive cursor c1 as 'select * from t1';
> --- relative is invalid when not positioned on a row
>  relative 0 c1;
>  close c1;
>  get scroll insensitive cursor c1 as 'select * from t1';
> --- relative is invalid when not positioned on a row
>  relative 2 c1;
>  close c1;
>  
> -
>  -- positive
>  
>  -- test positioning
> Index: java/testing/org/apache/derbyTesting/functionTests/master/DerbyNet/scrollCursors1.out
> ===================================================================
> --- java/testing/org/apache/derbyTesting/functionTests/master/DerbyNet/scrollCursors1.out	(revision 178761)
> +++ java/testing/org/apache/derbyTesting/functionTests/master/DerbyNet/scrollCursors1.out	(working copy)
> @@ -34,18 +34,15 @@
>  IJ ERROR: RELATIVE is not allowed on a forward only cursor.
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- 0 is invalid value for absolute
> -absolute 0 c1;
> -IJ ERROR: 0 is an invalid value for ABSOLUTE <integer> <cursorname>
> +ij> absolute 0 c1;
> +No current row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 0 c1;
> +ij> relative 0 c1;
>  ERROR (no SQLState): Cursor is Not on a Valid Row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 2 c1;
> +ij> relative 2 c1;
>  ERROR (no SQLState): Cursor is Not on a Valid Row
>  ij> close c1;
>  ij> -- positive
> Index: java/testing/org/apache/derbyTesting/functionTests/master/DerbyNetClient/scrollCursors1.out
> ===================================================================
> --- java/testing/org/apache/derbyTesting/functionTests/master/DerbyNetClient/scrollCursors1.out	(revision 178761)
> +++ java/testing/org/apache/derbyTesting/functionTests/master/DerbyNetClient/scrollCursors1.out	(working copy)
> @@ -34,19 +34,18 @@
>  IJ ERROR: RELATIVE is not allowed on a forward only cursor.
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- 0 is invalid value for absolute
> -absolute 0 c1;
> -IJ ERROR: 0 is an invalid value for ABSOLUTE <integer> <cursorname>
> +ij> absolute 0 c1;
> +No current row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 0 c1;
> -ERROR (no SQLState): Cursor is Not on a Valid Row
> +ij> relative 0 c1;
> +No current row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 2 c1;
> -ERROR (no SQLState): Cursor is Not on a Valid Row
> +ij> relative 2 c1;
> +C50 |I          
> +-----
> +c |3          
>  ij> close c1;
>  ij> -- positive
>  ----- test positioning
> Index: java/testing/org/apache/derbyTesting/functionTests/master/scrollCursors1.out
> ===================================================================
> --- java/testing/org/apache/derbyTesting/functionTests/master/scrollCursors1.out	(revision 178761)
> +++ java/testing/org/apache/derbyTesting/functionTests/master/scrollCursors1.out	(working copy)
> @@ -34,19 +34,18 @@
>  IJ ERROR: RELATIVE is not allowed on a forward only cursor.
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- 0 is invalid value for absolute
> -absolute 0 c1;
> -IJ ERROR: 0 is an invalid value for ABSOLUTE <integer> <cursorname>
> +ij> absolute 0 c1;
> +No current row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 0 c1;
> -ERROR X0X87: ResultSet.relative(int row) cannot be called when the cursor is not positioned on a row.
> +ij> relative 0 c1;
> +No current row
>  ij> close c1;
>  ij> get scroll insensitive cursor c1 as 'select * from t1';
> -ij> -- relative is invalid when not positioned on a row
> -relative 2 c1;
> -ERROR X0X87: ResultSet.relative(int row) cannot be called when the cursor is not positioned on a row.
> +ij> relative 2 c1;
> +C50                                               |I          
> +--------------------------------------------------------------
> +c                                                 |3          
>  ij> close c1;
>  ij> -- positive
>  -- test positioning
> Index: java/client/org/apache/derby/client/am/ResultSet.java
> ===================================================================
> --- java/client/org/apache/derby/client/am/ResultSet.java	(revision 178761)
> +++ java/client/org/apache/derby/client/am/ResultSet.java	(working copy)
> @@ -1804,18 +1804,51 @@
>          // discard all previous updates when moving the cursor.
>          resetUpdatedColumns();
>  
> -        // this method may only be called when the cursor on a valid row,
> -        // not after the last row, before the first row, or on the insert row.
> -        // throw exception if result set contains no rows, because there is no current row.
> -        if (isBeforeFirstX() || isAfterLastX() || isOnInsertRow_ || resultSetContainsNoRows()) {
> +        // this method may not be called when the cursor on the insert row
> +        if (isOnInsertRow_) {
>              throw new SqlException(agent_.logWriter_, "Cursor is Not on a Valid Row");
>          }
>  
> +        // If the resultset is empty, relative(n) is a null operation
> +        if (resultSetContainsNoRows()) {
> +            isValidCursorPosition_ = false;
> +            return isValidCursorPosition_;
> +        }
> +        
> +        // relative(0) is a null-operation, but the retruned result is
> +        // dependent on wether the cursorposition is on a row or not.
>          if (rows == 0) {
> -            isValidCursorPosition_ = true;
> +            if (isBeforeFirstX() || isAfterLastX()) {
> +                isValidCursorPosition_ = false;
> +            } else {
> +                isValidCursorPosition_ = true;
> +            }
>              return isValidCursorPosition_;
>          }
>  
> +        // Handle special cases when the cursor is before first or
> +        // after last, since the following code assumes we ar on a
> +        // valid cursor
> +        if (isBeforeFirstX()) {
> +            if (rows > 0) {
> +                nextX();
> +                return relativeX(rows-1);
> +            } else {
> +                isValidCursorPosition_ = false;
> +                return isValidCursorPosition_;
> +            }
> +        }
> +        if (isAfterLastX()) {
> +            if (rows < 0) {
> +                previousX();
> +                return relativeX(rows+1);
> +            } else {
> +                isValidCursorPosition_ = false;
> +                return isValidCursorPosition_;
> +            }
> +        }
> +        // Ok, now we are on a row and ready to do some real positioning.....
> +
>          resetRowsetFlags();
>  
>          // currentAbsoluteRowNumber is used for static cursors only.

> M      java/tools/org/apache/derby/impl/tools/ij/utilMain.java
> M      java/engine/org/apache/derby/impl/sql/execute/ScrollInsensitiveResultSet.java
> M      java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors2.java
> M      java/testing/org/apache/derbyTesting/functionTests/tests/lang/scrollCursors1.sql
> M      java/testing/org/apache/derbyTesting/functionTests/master/DerbyNet/scrollCursors1.out
> M      java/testing/org/apache/derbyTesting/functionTests/master/DerbyNetClient/scrollCursors1.out
> M      java/testing/org/apache/derbyTesting/functionTests/master/scrollCursors1.out
> M      java/client/org/apache/derby/client/am/ResultSet.java


-- 
Bernt Marius Johnsen, Database Technology Group, 
Sun Microsystems, Trondheim, Norway