orderedcolumn.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.sql.compile.OrderedColumn

   Copyright 1998, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package	org.apache.derby.impl.sql.compile;

import org.apache.derby.iapi.services.sanity.SanityManager;

/**
 * An ordered column has position.   It is an
 * abstract class for group by and order by
 * columns.
 *
 * @author jamie
 */
public abstract class OrderedColumn extends QueryTreeNode 
{
	protected static final int UNMATCHEDPOSITION = -1;
	protected int	columnPosition = UNMATCHEDPOSITION;

	/**
	 * Indicate whether this column is ascending or not.
	 * By default assume that all ordered columns are
	 * necessarily ascending.  If this class is inherited
	 * by someone that can be desceneded, they are expected
	 * to override this method.
	 *
	 * @return true
	 */
	public boolean isAscending()
	{
		return true;
	}

	/**
	 * Convert this object to a String.  See comments in QueryTreeNode.java
	 * for how this should be done for tree printing.
	 *
	 * @return	This object as a String
	 */
	public String toString() 
	{
		if (SanityManager.DEBUG)
		{
			return "columnPosition: " + columnPosition + "\n" +
				super.toString();
		}
		else
		{
			return "";
		}
	}

	/**
	 * Get the position of this column
	 *
	 * @return	The position of this column
	 */
	public int getColumnPosition() 
	{
		return columnPosition;
	}

	/**
	 * Set the position of this column
	 *
	 * @return	Nothing
	 */
	public void setColumnPosition(int columnPosition) 
	{
		this.columnPosition = columnPosition;
		if (SanityManager.DEBUG)
		{
			SanityManager.ASSERT(columnPosition > 0,
				"Column position is " + columnPosition +
				". This is a problem since the code to generate " +
				" ordering columns assumes it to be one based -- i.e. "+
				" it subtracts one");

		}
	}
}