Prodataset : Fill() Method using Index.

A dataset's queries can be controlled by using your own query, or by using data-source-handle:FILL-WHERE-STRING. Here is a small example that does both, for the sports db.

def temp-table ttcust field cust-num as int field name as char.
def temp-table ttord  field cust-num as int field order-num as int.
def dataset ds for ttcust,ttord
  data-relation r1 for ttcust,ttord relation-fields(cust-num,cust-num).

def query qcust for customer.

query qcust:query-prepare("for each customer by cust-num desc").

def data-source dcust for query qcust.
def data-source dord for order.
buffer ttcust:attach-data-source(data-source dcust:handle).
buffer ttord:attach-data-source(data-source dord:handle).

data-source dord:fill-where-string = "where order.cust-num = ttcust.cust-num by
order-num desc".

dataset ds:fill.

for each ttcust:
   disp ttcust.cust-num.
   for each ttord where ttord.cust-num = ttcust.cust-num.
      disp ttord.cust-num  ttord.order-num.
   end.
end.

Thanks Mary,

    I got the records in descending order.

   But Still I am confuse about use of index in Fill method of Dataset.

Regards

Vishwdeep

The FILL method will use the same Index Selection rules that the rest of the ABL uses. If you specify a query for the FILL then the compiler will determine which index to use based on the WHERE in your query. If there is no query, then the compiler will pick an index (most likely the primary index).

There is a KB article that explains the index selection rules that the ABL uses - P7066 explains some of the criteria behind selection and the 'OpenEdge Data Management: Database Design : Progress 4GL Index Usage' document explains how indexes are selected.

Thanks  Kevin.

In addition, I would think that how the records in the database data-source are accessed would be irrelevant.  What you care about is how the records in the dataset temp-tables are accessed.   In the example I gave, the dataset temp-tables had no index, so they were "roughly" in the order they were created.  If you want to see them in some particular order, it would be far better to put an index on the temp-tables (e.g. cust-num descending).   You cannot depend on the order used in the FILL, and sorting in reverse order during the FILL is probably a waste of time.

"Deleted" because Mary'd already answered the question.