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/impl/document/viewing/ExprMetaUtil.java
for ( int level = 0; level <= groups.size( ); level++ )
		{
			if ( level == 0 )
				groupDefn = queryDefn;
			else
				groupDefn = (IGroupDefinition) groups.get( level - 1 );
			prepareGroup( groupDefn, level, exprMetaList );
		}
		return exprMetaList;
	}
	
	/**
	 * Extract the expression information from group definition
	 * 
	 * @param trans
	 * @param groupLevel
	 * @param exprMetaList
	 * @throws DataException
	 */
	private void prepareGroup( IBaseTransform trans, int groupLevel, List exprMetaList )
	{
		Map exprMap = trans.getResultSetExpressions( );
		if ( exprMap == null )
			return;
		
		Iterator it = exprMap.keySet( ).iterator( );
		while ( it.hasNext( ) )
		{
			String exprName = (String) it.next( );
			IBaseExpression baseExpr = (IBaseExpression) exprMap.get( exprName );