see
functional index
On Wed, 25 Oct 2000 13:26:51 -0400
"Will Fitzgerald" <fitzgerald(at)inetmi(dot)com> wrote:
> I have a table, login, which has a field by the same name; there's an index
> on that field. I was surprised to discover that a SELECT which compares the
> login field to a constant uses an Index scan, but if it is compared to a
> function call--for example, lower()--a sequence scan is forced.
>
> Any idea why?
--
* Hosokawa Tetsuichi
* hosokawa(at)good-day(dot)co(dot)jp