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Re: Table clustering idea

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Luke Lonergan <llonergan(at)greenplum(dot)com>
Cc: Dawid Kuroczko <qnex42(at)gmail(dot)com>,Postgres Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Table clustering idea
Date: 2006-06-27 16:39:45
Message-ID: (view raw or whole thread)
Lists: pgsql-hackers
On Mon, Jun 26, 2006 at 11:31:24PM -0700, Luke Lonergan wrote:
> Jim,
> On 6/26/06 8:15 PM, "Jim C. Nasby" <jnasby(at)pervasive(dot)com> wrote:
> > On a somewhat related note, I think that it would be advantageous if the
> > FSM had a means to prefer certain pages for a given tuple over other
> > pages. This would allow for a better way to keep heap and possibly index
> > data more compacted, and it would also be a means of keeping tables
> > loosely clustered. It would also make it far easier to shrink heaps that
> > have become bloated, because the FSM could be told to favor pages at the
> > beginning of the relation.
> Interesting idea - page affinity implemented using the FSM.
> WRT feasibility of BTREE organized tables, I'm not sure I see the problem.
> Teradata implemented a hashing filesystem for their heap storage and I've
> always wondered about how they handle collision and chaining efficiently,
> but it's a solved problem for sure - knowing that makes the challenge that
> much easier :-)

I know there were discussions in the past, though as per usual I can't
find them in the archives. At one point I had suggested clustering not
on a row level, but on a page level, since it doesn't really matter
terribly if the tuples in a page are clustered (worst case you can scan
the entire page).

I think one of the issues might have been: how will you handle other
indexes on the table when you can no longer point them at an item (since
items will need to move to maintain an IOT).
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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