| From: | Shaun Thomas <sthomas(at)optionshouse(dot)com> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | Mike Christensen <mike(at)kitchenpc(dot)com>, "Schnabel, Robert D(dot)" <schnabelr(at)missouri(dot)edu>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: When does CLUSTER occur? |
| Date: | 2012-11-29 18:28:55 |
| Message-ID: | 50B7A967.2000904@optionshouse.com |
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| Lists: | pgsql-general |
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.
--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas(at)optionshouse(dot)com
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