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/ExprManagerUtil.java
.equals( "_rowPosition" );
	}
	/**
	 * 
	 * @param source
	 * @return
	 * @throws DataException 
	 */
	private void validateNodes( Node[] source ) throws DataException
	{
		Node[] preparedNodes = populateNodeList( source );
		for ( int i = 0; i < preparedNodes.length; i++ )
		{
			isValidNode( preparedNodes[i], preparedNodes[i] );
		}
	}
	/**
	 * 
	 * @param startNode
	 * @param candidateNode
	 * @return
	 * @throws DataException 
	 */
	private void isValidNode( Node startNode, Node candidateNode ) throws DataException
	{
		
		Object[] nodes = startNode.getChildren( ).toArray( );
		for ( int i = 0; i < nodes.length; i++ )
		{
			if ( candidateNode.equals( nodes[i] )