Re: Much Ado About COUNT(*)

On Tue, 2005-01-18 at 12:45 -0800, Sailesh Krishnamurthy wrote:
> >>>>> "Jonah" == Jonah H Harris <jharris(at)tvi(dot)edu> writes:
>
> Jonah> Replying to the list as a whole:
>
> Jonah> If this is such a bad idea, why do other database systems
> Jonah> use it? As a businessperson myself, it doesn't seem
> Jonah> logical to me that commercial database companies would
> Jonah> spend money on implementing this feature if it wouldn't be
> Jonah> used. Remember guys, I'm just trying to help.
>
> Systems like DB2 don't implement versioning schemes. As a result there
> is no need to worry about maintaining visibility in
> indexes. Index-only plans are thus viable as they require no change in
> the physical structure of the index and no overhead on
> update/delete/insert ops.
>
> I don't know about Oracle, which I gather is the only commercial
> system to have something like MVCC.
>

Perhaps firebird/interbase also? Someone mentioned that on these lists,
I'm not sure if it's true or not.

I almost think to not supply an MVCC system would break the "I" in ACID,
would it not? I can't think of any other obvious way to isolate the
transactions, but on the other hand, wouldn't DB2 want to be ACID
compliant?

Regards,
Jeff Davis