Re: When does CLUSTER occur? - Mailing list pgsql-general

From Mike Christensen
Subject Re: When does CLUSTER occur?
Date
Msg-id CABs1bs19Kbf-hn_TOkgw-wsSjc-K1xjGYS6YFjRqwE94WsUbaQ@mail.gmail.com
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In response to Re: When does CLUSTER occur?  (Shaun Thomas <sthomas@optionshouse.com>)
Responses Re: When does CLUSTER occur?  (Serge Fonville <serge.fonville@gmail.com>)
Re: When does CLUSTER occur?  (Igor Neyman <ineyman@perceptron.com>)
List pgsql-general

On Thu, Nov 29, 2012 at 10:28 AM, Shaun Thomas <sthomas@optionshouse.com> wrote:
On 11/29/2012 12:20 PM, Jeff Janes wrote:

It would maintain an imperfect clustering, but still much better than
current behavior.

I thought about that, too. The "imperfect clustering" made me erase everything I'd written. If the clustering is imperfect, it's not really clustering. It would mean less random reads to restart the seek chain though, so it would be a perceptible gain. But it's still not real clustering until the order is maintained indefinitely.

So far as I know, that simply can't be done with MVCC. Especially on an insert-only table that's clustered on a column unrelated to insert order.


How is this implemented in MS SQL then?  Obviously, MS SQL supports real clustering and has MVCC..

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