At 12:48 PM 1/13/2003 +0100, Pete Clark wrote:

> >The number of indexes is not all too important, what matters is their
> >selectivity.

>Is there some sort of way of figuring out what the 'boundary' is?
>
>Like, a spread of 50% ( a boolean field ) is obviously silly. But what
>sort of percentage should I drop to, before actually creating an index?

Like so many things, the appropriate selectivity depends on usage.
If your data is archival, then non-selective indexes aren't a great
problem. If you delete rows or change the value of the indexed
field, non-selective indexes introduce performance problems with
garbage collection.


Regards,

Ann
www.ibphoenix.com
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