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Re: Much Ado About COUNT(*)

From: Jeff Davis <jdavis-pgsql(at)empires(dot)org>
To: sailesh(at)cs(dot)berkeley(dot)edu
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Much Ado About COUNT(*)
Date: 2005-01-18 22:10:48
Message-ID: 1106086248.2886.539.camel@jeff (view raw or flat)
Thread:
Lists: pgsql-announcepgsql-hackerspgsql-patches
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


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