Bug 201013 [Automation][Regression]Invalid group key column name: _{$TEMP_GROUP_1$} occurs when preview attached report[1102]
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
IResultObjectEvent objectEvent = new ComputedColumnHelper( this.dataSet,
					computedColumns,
					temporaryComputedColumns );
			odiQuery.addOnFetchEvent( objectEvent );
			this.dataSet.getComputedColumns( )
					.addAll( temporaryComputedColumns );
		}
		if ( dataSet.getEventHandler( ) != null )
		{
			OnFetchScriptHelper event = new OnFetchScriptHelper( dataSet );
			odiQuery.addOnFetchEvent( event );
		}
		if ( dataSetFilters.size( )
				+ queryFilters.size( ) + multipassFilters.size( ) > 0 )
		{
			IResultObjectEvent objectEvent = new FilterByRow( dataSetFilters,
					queryFilters,
					multipassFilters,
					dataSet );
			odiQuery.addOnFetchEvent( objectEvent );
		}
	}
	
	/**
	 * get the data type of a expression
	 * @param cx
	 * @param expr
	 * @return
	 * @throws DataException 
	 */