Bug 196745 Data Engine implementation of BPS80- Result Set Sharing
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ResultIterator.java
/**
		 * The method which extracts column name from group definition.
		 * 
		 * @param group
		 * @return
		 */
		private String getGroupKeyExpression( GroupDefinition group )
		{
			String columnName;
			if ( group.getKeyColumn( ) != null )
			{
				columnName = ExpressionUtil.createJSRowExpression( group.getKeyColumn( ) );
			}
			else
			{
				columnName = group.getKeyExpression( );
			}	
		
			return columnName;
		}
	}
	
	/**
	 * Util class to help ResultIterator to save data into report document
	 */
	class RDSaveHelper
	{
		
		private DataEngineContext context;
		private IBaseQueryDefinition queryDefn;