Indexing or sorting ordered arrays.

[Ruslan Zasukhin]

On 11/20/05 9:31 AM, "Ed Kleban" <Ed at Kleban.com> wrote:

> When you set the fIndexed EVFlag, then V2 builds an index, correct?

> Presumably it uses some sort algorithm to do this.   Similarly when you call
> the Vtable.Sort command, it again uses some algorithm to sort.  I am curious
> what the algorithm used is, because I would like to know the behavior when
> the column of items to index, or the column of items to sort is already
> sorted.  I'm curious if when the items are already sorted:

> 1) Performing a sort on them may be very slow, because QuickSort is used,
> and Quicksort has poor performance when used to sort a list that is already
> sorted, or...
> 
> 2)  Performing a sort on them is very fast because a serialization check is
> made to see if they are already sorted and if so nothing is done, or...
 
> 3) Performing a sort on them is not terrible, because IntroSort is used
> instead of QuickSort which has much better worst-case sorting efficiency
> when the list is already sorted, or...
> 
> 4) QuickSort is used, however before it is use several of list elements are
> randomly reordered to avoid the performance problems that occur when the
> list is already sorted.
> 
> 5) I'm totally clueless because you're simply not indexing or sorting in any
> of these ways.

Actually nature of DBMS indexing is sort of inserts.

For some cases of small sets we use just quicksort, but not recursive

-- 
Best regards,

Ruslan Zasukhin
VP Engineering and New Technology
Paradigma Software, Inc

Valentina - Joining Worlds of Information
http://www.paradigmasoft.com

[I feel the need: the need for speed]