Re: Performance of sequences as primary key generators.

From: Chrysalis <cellis_at_iol.ie>
Date: 1997/06/25
Message-ID: <33B17940.79CA@iol.ie>#1/1

Ben Harmon wrote:
>
> A sequence, as I understand it, is actually just another table that is being
> incremented by a procedure that is run when the NEXTVAL statement is issued.
> (snip)

No, each sequence is implemented as system-level memory cache. There is no table updating involved, so performance is generally good.

The only disadvantage perceived by some users is that, once allocated, a sequence number cannot be re-used, even if the user transaction to which it was allocated fails. Thus, "gaps" can appear in generated sequences. This is not a problem in the majority of uses.

Hope this helps.

Chrysalis

FABRICATI DIEM, PVNC
('To Protect and to Serve')
Terry Pratchett : "Guards Guards" Received on Wed Jun 25 1997 - 00:00:00 CDT