At 10:04 AM 9/18/2000 +1100, Ron Burnett wrote:
>Greetings everyone,
>
>A question for the IMAGE gurus:
>
>For many years we have had a PMI (Patient Master Index) with a
>primary key of X6 wihch contains an all numeric identifier in the
>range of 100000 to (now) about 940000.  This has served us very
>well, with pretty good retrieval performance, even with a severely
>overloaded system.
>
>However, we estimate that we are going to hit the 1000000 mark
>in issued numbers within the next 14 to 18 months.  Time to think
>about expanding that X6 to an X8.

I would suggest that you take a close look at integer keys. The most likely
type to convert to would be K2.

WARNING!!
Because the primary entry location is calculated as the numeric value
modulo the capacity, you can get into a terrible mess if your capacity is
ever less than HighestKeyValue - LowestKeyValue.  As long as you don't
break this rule, they (integer keys) work extremely well.



Advantages:
- saves space (disc space is always an issue, or at least keeps returning
as one)
- uses a simpler algorithm for entry addressing ( value modulo the capacity ).

Disadvantages:
- none, unless Capacity < (HighestKeyValue - LowestKeyValue)

Brian Duncombe  [log in to unmask]  http://www.triolet.com
voice: 1-877-TRIOLET (874-6538) (905)632-2773 fax: (905) 632-8704
"Inside every large program is a small one struggling to get out"
C.A.R. Hoare