Thank you for your responses. I'm beginning to suspect that just touching
a key in the SQL, even if you write your conditions to never check it,
causes the SQL engine to build/select indexes that would let it use that
key. I think we'll have to write multiple cursor declarations or code it
as a dynamic statement for best performance.
From: darren@xxxxxxxxx
To: "midrange-RPG RPG message board" <rpg400-l@xxxxxxxxxxxx>
Date: 08/11/2011 01:32 PM
Subject: Conditional SQL processing against host variables
Sent by: rpg400-l-bounces@xxxxxxxxxxxx
Using something like the following statement, we take a pretty high
performance hit compared to writing multiple cursors for times when the
user has selected a wildcard (*ANY) as shown below. I suspect that the SQL
is actually looking for TUSER='*ANY' even though it will never find it, and
its not necessary. Is there a better way to condition this type of
operation? I'm aware of dynamic SQL, but its a bit of a pain for larger
statements.
/FREE
exec sql declare C1 cursor for
Select TWS
TUSER,
TTDTE
from TFILE
where (TWS = :Device or :Device = '*ANY')
And (TUser = :User or :User = '*ANY')
/END-FREE
--
This is the RPG programming on the IBM i / System i (RPG400-L) mailing list
To post a message email: RPG400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit:
http://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at
http://archive.midrange.com/rpg400-l.
midrange.com
