VMS 6.2, Dec Rdb V6.1-13, Powerhouse 7.10E6

[Bob Deskin]

This applies generally to relational support in PowerHouse.

How much an index will help depends on what the database decides to do. We 
do not explicitly use the index in PowerHouse, although we do use the 
index to determine sequence (ORDER BY). We send the request to the 
database and it decides whether using the index is more efficient. It's 
going to depend on how many rows are retrieved, how many rows are in the 
table, whether the index is unique or repeating and how long the chains 
are, etc. So, as in all cases, I suggest some testing is in order.

Bob


Bob Deskin
Senior Product Manager
Application Development Tools
COGNOS, an IBM company
+1 613-738-1338 ext 7268
bob.deskin at ca.ibm.com
http://powerhouse.cognos.com




"Penney, John" <resolutebay at yahoo.com> 
Sent by: powerh-l-bounces+bob.deskin=ca.ibm.com at lists.sowder.com
2008-04-22 10:04 am

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VMS 6.2, Dec Rdb V6.1-13, Powerhouse 7.10E6






Powerhouse Listers:
 
Working on a system with the above parameters. Yes, not supported, but I 
digress. I am analyzing some performance issues and need some advice 
regarding CHOOSE on a non-keyed field (column) which one can do because 
it's a relational database. Can one expect a significant improvement in 
performance if said column was declared as an Index?
 
In adhoc tests I have found about a 10% improvement in throughput using a 
CHOOSE on a non-Indexed column versus a SELECT. What can I expect if it's 
Indexed?
 
Would somebody please share with me their experiences in these instances.
 
Many thanks!
 
JP in IL
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