At 10:23 PM 97/11/05 -0700, John Pearce wrote:
>I need to add a new key to an Image detail dataset.  The key is a single
>character with five values (0-4).  About 80% of the 85,000 records will
>have the same key value (0) and thus a long, long chain.  The remaining
>17,000 records should be spread about equally through the other four
values
>and still long chains.
>
>I recall someone posted a technique to overcome the long chains situation.
>Unfortunately, it appears that was one message I didn't archive. :(  If
>someone has the original message or knows the technique, could you please
>send it to me via e-mail?  Thanks!

The only solution I can think of is to use a third-party indexing tool.  As
far as I know both SUPERDEX and Omnidex have the ability to index a value,
unless the field is blank.  So, in your case, if you leave the field blank
when it is the "default" or "common" value no index would be created.  A
simple DBFIND on the item with the other 4 values will return the approp
riate records, and a serial read, which through coding you would skip the
non-blank records, would be used for the other records.

If you don't have a TPI product, a non-IMAGE solution that I can think of
is to use SUPRTOOL.  Your set is not really that big and SUPRTOOL can read
through the set in about 15% of your serial read timing.  However, if you
have to have the records on line, this won't work well.

Gilles Schipper's solution of two sets will work, but as he points out,
this is somewhat against common database design standards.  Because your
set is small (relative to the ability of IMAGE and the 3k), I would
recommend *not* doing this.  I believe your future management and support
issues (say 3 years from now) will not make it worth it.  Sticking to
standard designs will not cause someone to say, "Hey, why was this done?"
in 3 years.

My $.02.

LB
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        /  /                 Larry Boyd
HEWLETT/hp/PACKARD           Commercial Systems Division (CSY)
      /__/                   mailto:Larry_Boyd.hp.com
                             (408)447-4127

"All my life I wanted to be somebody.
     Now I realize I should have been more specific."
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