| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | "Jim C(dot) Nasby" <jim(at)nasby(dot)net> |
| Cc: | Robert Treat <xzilla(at)users(dot)sourceforge(dot)net>, pgsql-patches(at)postgresql(dot)org, Guillaume Smet <guillaume(dot)smet(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: Have vacuum emit a warning when it runs out of maintenance_work_mem |
| Date: | 2007-05-13 10:19:07 |
| Message-ID: | 4646E61B.1030202@enterprisedb.com |
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| Lists: | pgsql-patches |
Jim C. Nasby wrote:
> On Sat, May 12, 2007 at 07:57:44PM +0100, Heikki Linnakangas wrote:
>> Or we could switch to a more compact representation of the dead tuples,
>> and not need such a big maintenance_work_mem in the first place.
>
> Sure, but even with a more compact representation you can still run out
> of maintenance_work_mem... unless we allow this to spill to disk. At
> first guess that sounds insane, but if you've got a large enough set of
> indexes it *might* actually be faster.
It would only make sense if the table is clustered on an index, so that
you'd in practice only need to keep part of the array in memory at a
time. It's pretty narrow use case, not worth spending time on I think.
> Either way, as long as maintenance_work_mem is an issue I think we need
> a way to warn users.
I agree.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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