Bug 189706 Enhance computed column aggregation function handling in UI.
Due to the issue discussed in 189705, current computed column aggregation builder in data set editor has bugs to extend: 1.When new a computed column, the aggregation argument field cannot be correctly set. 2.The argument field cannot be correct grayed out when user select a aggregation function without arguments 3.The available aggregation function list is incomprehensive 4.Some aggregation function cannot be set to model(say, weightedAve).
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ComputedColumnHelper.java
value );
				}
				else
				{
					throw new DataException( ResourceConstants.EXPR_INVALID_COMPUTED_COLUMN,
							resultObject.getResultClass( )
									.getFieldName( columnIndexArray[i] ) );
				}
			}
		}
		finally
		{
			Context.exit( );
		}
		logger.exiting( ComputedColumnHelper.class.getName( ), "process" );
		return true;
	}
	/**
	 * Indicate the ComputedColumnHelper to reprepare.
	 * 
	 * @param rePrepare
	 */
	public void setRePrepare( boolean rePrepare )
	{
		this.isPrepared = !rePrepare;
	}
	/**
	 * Convert ccList to projComputedColumns, only prepare once.
	 */
	private void prepare( IResultClass resultClass ) throws DataException