Bug 131011 Support running query based on report document data
Data Engine should support running a query based on data set and expression data stored in a report document. This bugzilla entry serves as a repository for design docs and notes related to this feature.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/executor/transform/group/GroupBy.java
throws DataException
	{
		if ( previousGroupKey == currentGroupKey )
			return true;
		if ( previousGroupKey == null || currentGroupKey == null )
			return false;
		return isSameGroup( currentGroupKey, previousGroupKey );
	}
	/**
	 * If the currentGroupKey and previousGroupKey is not null, compare these
	 * two key values
	 * 
	 * @param currentGroupKey
	 * @param previousGroupKey
	 * @return boolean
	 * @throws DataException
	 */
	abstract boolean isSameGroup( Object currentGroupKey,
			Object previousGroupKey ) throws DataException;
	/**
	 * Returun whether start group value is needed
	 * 
	 * @return yes, start group value is needed
	 */
	boolean needsGroupStartValue( )
	{
		return false;
	}
	/**
	 * Gets the index of the column to group by