Bug 145022 Provide a utility method to help GUI enhance aggregate on.
DtE will provide a method hasAggregation(String expression) in org.eclipse.birt.core.data.ExpressionUtil, and the return value will be true when the expression is a valid JS expression and it has aggregation defined.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/ExpressionParserUtility.java
int index = getFunctionIndex( child.getString( ), tree );
				compileFunctionNode( tree.getFunctionNode( index ),
						tree,
						columnExprList );
			}
			
			
			Node nextChild = child.getNext( );
			
			if ( child.getType( ) == Token.NUMBER
					|| child.getType( ) == Token.STRING
					|| child.getType( ) == Token.TRUE
					|| child.getType( ) == Token.FALSE
					|| child.getType( ) == Token.NULL )
			{
				processChild( complexNode, child, tree, columnExprList );
				child = nextChild;
				continue;
			}
			processChild( complexNode, child, tree, columnExprList );
			child = nextChild;
		}
	}
	/**
	 * compile the function expression
	 * 
	 * @param node
	 * @param tree
	 * @param columnExprList
	 * @throws BirtException