Bug 206279 Removed computed cols listed in expression builder[07]
Description: Removed computed column listed in expression builder inside DataSet Editor dialog Build number:2.2.2.v20071011 Steps to reproduce: 1. New data source and dataset. 2. Add a computed column in dataset and click OK. 3. Open the dataset, remove the computed column. 4. Add a new computed column and check columns in available Data Sets. Expected result: The removed computed column isn't there. Actual result: The removed computed column is still there for selection. Error log:n/a
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
{
	private static DataSetProvider instance = null;
	
	private transient Hashtable htColumns = new Hashtable( 10 );
	private static Hashtable htDataSourceExtensions = new Hashtable( 10 );
	private transient Hashtable sessionTable = new Hashtable( 10 );
	
	private static final char RENAME_SEPARATOR = '_';
	private static String UNNAME_PREFIX = "UNNAMED"; 
	/**
	 * @return
	 */
	private static DataSetProvider newInstance( )
	{
		return new DataSetProvider( );
	}
	/**
	 * 
	 * @return
	 */
	public static DataSetProvider getCurrentInstance( )
	{
		if ( instance == null )
			instance = newInstance( );
		return instance;
	}
	/**
	 * get columns data by data set name
	 * @param dataSetName