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Re: Much Ado About COUNT(*)

From: Christopher Browne <cbbrowne(at)acm(dot)org>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Much Ado About COUNT(*)
Date: 2005-01-19 05:09:53
Message-ID: m3mzv60ztq.fsf@knuth.knuth.cbbrowne.com (view raw or flat)
Thread:
Lists: pgsql-announcepgsql-hackerspgsql-patches
Martha Stewart called it a Good Thing when jdavis-pgsql(at)empires(dot)org (Jeff Davis) wrote:
> 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?

Wrong, wrong, wrong...

MVCC allows an ACID implementation to not need to do a lot of resource
locking.

In the absence of MVCC, you have way more locks outstanding, which
makes it easier for there to be conflicts between lock requests.

In effect, with MVCC, you can do more things concurrently without the
system crumbling due to a surfeit of deadlocks.
-- 
"cbbrowne","@","gmail.com"
http://www3.sympatico.ca/cbbrowne/multiplexor.html
Why isn't phonetic spelled the way it sounds?

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