>no one have any explanation ?
>
>what i don't understand is that in select IDObj From DESCRIPTION where ID='ID_NOT_EXIST'
>the speed is slow when no record are founded (so the number of field/size in table
>Description must not matter, only the size of the index) ! but it's not the case, i do
>several test to confirm it ....
>
>so it's mean that the data of the index is stored INSIDE the page of the record ??

Don't think I can shed any light, but one small question:

Is your query,

select IDObj From DESCRIPTION where ID='ID_HAS_NEVER_EXISTED', or
select IDObj From DESCRIPTION where ID='ID_THAT_IS_RECENTLY_DELETED_UPDATED_OR_ADDED'?

I don't think the index holds any versioning information, so if the ID is visible from another transaction OR the record has been deleted but not yet garbage collected, then I would expect the query to have to look at the data and not just the index (though I could be wrong, I've never looked into this).

HTH,
Set