| From: | Bernd Helmle <mailings(at)oopsware(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Subject: | Re: Automatic free space map filling |
| Date: | 2006-03-02 09:02:58 |
| Message-ID: | 20060302090258.GA29605@sparkey.oopsware.intra |
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| Lists: | pgsql-hackers |
[sorry to everyone if that mail arrives multiple times, but i had
some odd problems with my mail gateway yesterday...]
On Wed, Mar 01, 2006 at 12:41:01PM -0500, Tom Lane wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> > Tom Lane wrote:
> >> How does an optimistic FSM entry avoid the need to run vacuum?
>
> > It ensures that all freed tuples are already in the FSM.
>
> That has nothing to do with it, because the space isn't actually free
> for re-use until vacuum deletes the tuple.
>
But couldn't such an opportunistic approach be used for
another lightweight VACUUM mode in such a way, that VACUUM could
look at a special "Hot Spot" queue, which represents potential
candidates for freeing? Let's call it a 2-phase VACUUM....this would
avoid a constant long running VACUUM run on big tables, e.g. when
tuples gets updated (or deleted) frequently. Just an idea...
Bernd
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