Bug 200516 CachedQueryResults should also implement IQueryService.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
.equalsIgnoreCase( "dataSetRow._rowPosition" ) )
		{
			groupName = "_{$TEMP_GROUP_" + i + "ROWID$}_";
		}
		else
		{
			groupName = "_{$TEMP_GROUP_" + i + "$}_";
		}
		return groupName;
	}
	/**
	 * Get the computed column instance according to the group type.If group has
	 * interval, return GroupComputedColumn, otherwise return normal computed
	 * column.
	 * 
	 * @param cx
	 * @param groupSpecs
	 * @param i
	 * @param src
	 * @param expr
	 * @param groupName
	 * @param dest
	 * @return
	 * @throws DataException
	 */
	private IComputedColumn getComputedColumnInstance( Context cx,
			int interval, IGroupDefinition src,
			String expr, String groupName, IQuery.GroupSpec dest )
			throws DataException
	{