Bug 195970 Two issues when evaluate a query inlcuding a subquery[07]
Description: Currently, when evaluating a query which includes a subquery, the query will be evaluated twice. The binding of query will pass to subquery twice. If user write a java script such as new Date() and i++. The result of query will be incorrect. Another issue: when write the report document, the binding of query will be written twice and the performance is not good to evalulate it twice.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManager.java
* @param groupLevel
	 */
	public void addBindingExpr( String groupKey, Map resultsExprMap, int groupLevel )
	{
		if ( resultsExprMap == null )
			return;
		
		Context cx = Context.enter( );
		try
		{
			if ( groupKey != null )
			{
				CompiledExpression ce = ExpressionCompilerUtil.compile( groupKey,
						cx );
				if ( ce instanceof ColumnReferenceExpression )
				{
					ColumnReferenceExpression cre = ( (ColumnReferenceExpression) ce );
					groupKey = cre.getColumnName( );
				}
			}
			
			bindingExprs.add( new GroupBindingColumn( groupKey,
					groupLevel,
					resultsExprMap ) );
		}
		finally
		{
			Context.exit( );
		}
	}