| From: | Jim Nasby <decibel(at)decibel(dot)org> |
|---|---|
| To: | ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, "Jochem van Dieten" <jochemd(at)gmail(dot)com> |
| Subject: | Re: Dead Space Map for vacuum |
| Date: | 2007-01-05 21:44:27 |
| Message-ID: | BF8F559D-B21B-4334-A6B5-8AFAE1026631@decibel.org |
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| Thread: | |
| Lists: | pgsql-hackers |
On Jan 3, 2007, at 11:42 PM, ITAGAKI Takahiro wrote:
> BTW, if we want to achieve the index-only scan, we might have to do
> more
> aggressive VACUUM FREEZE. There were many comments that we should
> avoid
> vacuuming pages that contain only unfrozen tuples or a few dead
> tuples.
> I think it it true for efficient VACUUM, but the index-only scan
> does not
> work for the unfrozen pages. Which should we give priority?
Unless I'm mistaken, as soon as vacuum decides to dirty a page, the
only cost involved in freezing the page is CPU - and vacuum isn't
exactly a CPU-intensive process.
--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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