SET DESCENDING COMIX RDD vs Advantage CA-Clipper RDD

[astronm]

Can anyone tell me is it a good way to migrate from SET DESCENDING COMIX RDD to Advantage CA-Clipper RDD where
the following CA-Clipper 5.x functions or commands are not supported with Advantage:
1) The SET DESCENDING command is not supported.
2) The ordDescend() function is not supported.
We using this function allot especialy with reporting.
Thank you in advance.

 

[TonHu]

Write your own DESCENDING() function, or use the built-in Descend() function to 'revert' your keys. I guess for the ordDescend() there's no real alternative.

HTH
TonHu

 

[astronm]

Does it means that new index could be created?
In other words does it affect index order for other users.
"DESCENDING specifies that the index is to be built in decreasing order of value. Using this keyword is the same as specifying the DESCEND() function within <expKey>, but without the performance penalty during index updates.
If you create a DESCENDING index, you won't need to use the DESCEND() function during a SEEK. DESCENDING is an attribute of the index file, where it is stored and used for REINDEXing purposes.
This example uses DESCEND() in an INDEX expression to create a descending order date index:
USE Sales NEW
INDEX ON DESCEND(OrdDate) TO SalesDate

Later, use DESCEND() to SEEK on the descending index:

SEEK DESCEND(dFindDate)"(Guide to Ca-Clipper5.2)
Does it mean that DBSEEK (dFindDate) should work for ascend and DBSEEK DESCEND(dFindDate) for descend?
Thank you.

 

[JCreamerII]

A couple of thoughts, if you use the descend function, it can cause problems with an external module that doesn't have the descend function complied into the EXE, but has to read the index. I've bumped into that one. You can also go old school and subtract the date from a large number, that will also get you in reverse order.

Jim C.

 

[astronm]

Can we change the ascending/descending at runtime only?
(i.e., it does not change the descending flag stored on disk for the file).
Is it possible to replace this COMIX function : cmxDescend( [nOrder | cTag [, cBag [, lDescend]]] ) -> lPrevDescend ?
Thanks.

 

[astronm]

To write own DESCENDING() function - does it mean this could be a wrapper , or any example,please.
Thank you.