Bug 122854 There is redundant columns in "available columns" list in "export data" dialog.
Description: There is redundant columns in "available columns" list in "export data" dialog. Steps to reproduce: 1. Preview attached design in web viewer. 2. Select the table and click on "export" button. 3. There is a "detail" column name in "available columns" list which is not data set column.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
protected void handleCell( CellDesign cell, Object value )
		{
			
			for ( int i = 0; i < cell.getContentCount( ); i++ )
				cell.getContent( i ).accept( this, value );
		}
		/**
		 * A helper function for adding expression collection to stack
		 */
		protected void pushExpressions( Collection newExpressions )
		{
			this.expressionStack.addLast( this.expressions );
			this.expressions = newExpressions;
		}
		/**
		 * A helper function for removing expression collection from stack
		 */
		protected void popExpressions( )
		{
			assert !expressionStack.isEmpty( );
			this.expressions = (Collection) expressionStack.removeLast( );
		}
		/**
		 * A helper function for adding a query to query stack
		 */
		protected void pushQuery( IBaseTransform query )
		{
			this.queryStack.addLast( query );
		}
		/**