Re: Index & Constraint

Rajesh.Rao_at_jpmchase.com wrote:
>
> An example on my understanding of Reverse Key Indices:
>
> Say you have a table EMP with a column EMPNO, and an index on this
> field.This number is incremented sequentially for every new employee that
> joins in. And as employees retire, say, the records are deleted. This
> would generally mean deletion of records, with lower employee numbers. And
> subsequent deletion of indices. As such, deletions from the index are
> likely to be concentrated on a small set of leaf blocks towards the
> beginning of the index. A reverse key index, which reverses the bytes for
> the column value, could help in uniformly dividing the deletions across
> various branches of the index, and avoid a skewed index.
>
> Raj

Raj,

   I would rather tend to see the benefits in terms of contention avoidance when inserting (typically when the PK is sequence-generated), but by and large I share your view.

-- 
Regards,

Stephane Faroult
Oriole Software
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Author: Stephane Faroult
  INET: sfaroult_at_oriole.com

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