Handling large MRM messages

CREATE COMPUTE MODULE LargeMessageExampleFlow_Compute
	CREATE FUNCTION Main() RETURNS BOOLEAN
	BEGIN
		CALL CopyMessageHeaders();
  		-- Create a special folder in the output message to hold the input tree
  		-- Note : SourceMessageTree is the root element of an MRM parser
  		CREATE LASTCHILD OF OutputRoot.MRM DOMAIN 'MRM' NAME 'SourceMessageTree';

  		-- Copy the input message to a special folder in the output message
  		-- Note : This is a root to root copy which will therefore not build trees
  		SET OutputRoot.MRM.SourceMessageTree = InputRoot.MRM;

  		-- Create a special folder in the output message to hold the output tree
  		CREATE FIELD OutputRoot.MRM.TargetMessageTree;

  		-- Prepare to loop through the purchased items
  		DECLARE sourceCursor REFERENCE TO OutputRoot.MRM.SourceMessageTree.Invoice;
  		DECLARE targetCursor REFERENCE TO OutputRoot.MRM.TargetMessageTree;
  		DECLARE resultCursor REFERENCE TO OutputRoot.MRM;
  		DECLARE grandTotal   FLOAT     0.0e0;

  		-- Create a block so that it's easy to abandon processing
  		ProcessInvoice: BEGIN
    	-- If there are no Invoices in the input message, there is nothing to do
    	IF NOT LASTMOVE(sourceCursor) THEN
      		LEAVE ProcessInvoice;
    	END IF;

    	-- Loop through the invoices in the source tree
    	InvoiceLoop : LOOP
      		-- Inspect the current invoice and create a matching Statement
      		SET targetCursor.Statement =
        		THE ( 
          			SELECT
            			'Monthly'                        AS Type,
            			'Full'                           AS Style,
            			I.Customer.FirstName             AS Customer.Name,
            			I.Customer.LastName              AS Customer.Surname,
            			I.Customer.Title                 AS Customer.Title,
            			(SELECT 
              				FIELDVALUE(II.Title)  		AS Title,
              				II.UnitPrice * 1.6 			AS Cost,
              				II.Quantity                 AS Qty
            			FROM I.Purchases.Item[] AS II 
            			WHERE II.UnitPrice> 0.0                ) AS Purchases.Article[],
            			(SELECT
              				SUM( II.UnitPrice * 
                   			     II.Quantity  *
                   				 1.6                          )
            				FROM I.Purchases.Item[] AS II                      ) AS Amount,
            				'Dollars'                                  AS Amount.Currency
          				FROM sourceCursor AS I
          				WHERE I.Customer.LastName <> 'White'
       				 );

      		-- Turn the current Statement into a bit stream
      		-- The SET parameter is set to the name of the message set 
         -- containing the MRM definition
      		-- The TYPE parameter contains the path from the from the message 
         -- to element being serialized
      		-- The FORMAT parameter contains the name of the physical format 
         -- name defined in the message   
      		DECLARE StatementBitStream BLOB
        		ASBITSTREAM(targetCursor.Statement 
        			OPTIONS FolderBitStream
        			SET 'LargeMessageExample'
        			TYPE 'Data/Statement'
        			FORMAT 'XML1');
                
      		-- If the SELECT produced a result (that is, it was not filtered
         -- out by the WHERE clause), process the Statement
      		IF StatementBitStream IS NOT NULL THEN
        		-- create a field to hold the bit stream in the result tree
        		-- The Type of the element is set to MRM.BitStream to indicate
           -- to the MRM Parser that this is a bitstream 
        		CREATE LASTCHILD OF resultCursor
          			Type  MRM.BitStream
          			NAME  'Statement'
          			VALUE StatementBitStream;

        		-- Add the current Statement's Amount to the grand total
        		SET grandTotal = grandTotal + targetCursor.Statement.Amount;
      		END IF;

      		-- Delete the real Statement tree leaving only the bit stream version
      		DELETE FIELD targetCursor.Statement;

      		-- Step onto the next Invoice, removing the previous invoice and any
      		-- text elements that might have been interspersed with the Invoices
      		REPEAT
        		MOVE sourceCursor NEXTSIBLING;
        		DELETE PREVIOUSSIBLING OF sourceCursor;
      		UNTIL (FIELDNAME(sourceCursor) = 'Invoice') 
               OR (LASTMOVE(sourceCursor) = FALSE)
      		END REPEAT;

      		-- If there are no more invoices to process, abandon the loop
      		IF NOT LASTMOVE(sourceCursor) THEN
        		LEAVE InvoiceLoop;
      		END IF;

    	END LOOP InvoiceLoop;
  		END ProcessInvoice;

  		-- Remove the temporary source and target folders
  		DELETE FIELD OutputRoot.MRM.SourceMessageTree;
  		DELETE FIELD OutputRoot.MRM.TargetMessageTree;

  		-- Finally add the grand total
  		SET resultCursor.GrandTotal = grandTotal;
  		
  		-- Set the output MessageType property to be 'Data'
  		SET OutputRoot.Properties.MessageType = 'Data'; 
 
		RETURN TRUE;
	END;

	CREATE PROCEDURE CopyMessageHeaders() BEGIN
		DECLARE I INTEGER 1;
		DECLARE J INTEGER CARDINALITY(InputRoot.*[]);
		WHILE I < J DO
			SET OutputRoot.*[I] = InputRoot.*[I];
			SET I = I + 1;
		END WHILE;
	END;

END MODULE;