Progress 4GL - Enumerable.Take(TSource) Method in - progress-4gl

Question

Thanks in advance for looking at this question!
This is all in the context of a FOR EACH loop which can get quite lengthy - think 100,000 records - and I'm looking for a way to take n records from a position in that resultset e.g. start # 4000 & take the next 500 records.
I was looking around for keywords, in the ABL Reference, such as:
Position
LookAhead
RECID - Whether we can find a RECID at the nth position
Query Tuning
So far no luck. Any smarties out there with a hint?

Answer 1

Here is an example that I created against the sports database. The sports database is a sample database similar to the AdventureWorks database in SQL Server.
This should get you started:
def var v-query as char no-undo.
def var h as handle no-undo.
/* Here is where can set a dynamic query */
assign v-query = "for each orderline no-lock".
/* Create handle used for query */
create query h.
/* Set the table against the query so you can access it conveniently */
/* If you have other tables in your "for each", simply do a */
/* set-buffers on each table */
h:set-buffers(buffer orderline:handle).
/* Prepare Query */
h:query-prepare(v-query).
/* DO Open */
h:query-open.
/* Setup query to row 10 */
h:reposition-to-row(10).
LINE_LOOP:
repeat:
/* Read next row */
h:get-next.
/* Check if we are not past the end */
if h:query-off-end then leave LINE_LOOP.
/* Since we added orderline as a buffer we can now use it here */
disp orderline.ordernum
orderline.linenum
orderline.itemnum
orderline.price
orderline.qty.
end. /* repeat */
h:query-close.
FYI, the Progress Knowledge base and the PSDN have great samples and tutorials

Answer 2

other example - filling of dataset tables - BATCHING
DEFINE TEMP-TABLE ttOrder LIKE Order.
DEFINE DATASET dsOrder FOR ttOrder.
/* you can set a buffer object */
/*DEFINE DATA-SOURCE srcOrder FOR Order.*/
/* or you can set a query */
DEFINE QUERY qOrder FOR Order SCROLLING.
QUERY qOrder:QUERY-PREPARE ("FOR EACH Order").
DEFINE DATA-SOURCE srcOrder FOR QUERY qOrder.
BUFFER ttOrder:ATTACH-DATA-SOURCE( DATA-SOURCE srcOrder:HANDLE ).
/*The maximum number of ProDataSet temp-table rows to retrieve in each FILL operation.*/
BUFFER ttOrder:BATCH-SIZE = 10.
/* Empties the table before the FILL operation begins.
Without setting this attribute will next rows append to existing in temp-table */
BUFFER ttOrder:FILL-MODE = "EMPTY".
/* first time - result 1 - 10 */
DATASET dsOrder:FILL ().
FOR EACH ttOrder:
DISPLAY ttOrder.ordernum.
END.
/* set the startpoint to position 11 */
DATA-SOURCE srcOrder:RESTART-ROW = 11.
/* second time 11 - 20 */
DATASET dsOrder:FILL ().
FOR EACH ttOrder:
DISPLAY ttOrder.ordernum.
END.