| From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
|---|---|
| To: | Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> |
| Cc: | Greg Stark <greg(dot)stark(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [WIP] In-place upgrade |
| Date: | 2008-11-05 18:16:12 |
| Message-ID: | 20081105181612.GB3531@svana.org |
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| Lists: | pgsql-hackers |
On Wed, Nov 05, 2008 at 03:04:42PM +0100, Zdenek Kotala wrote:
> Greg Stark napsal(a):
> It is exceptional case between V3 and V4 and only on heap, because you save
> in varlena. But between V4 and V5 we will lost another 4 bytes in a page
> header -> page header will be 28 bytes long but tuple size is same.
>
> Try to get raw free space on each page in 8.3 database and you probably see
> a lot of pages where free space is 0. My last experience is something about
> 1-2% of pages.
Is this really such a big deal? You do the null-update on the last
tuple of the page and then you do have enough room. So Phase one moves
a few tuples to make room. Phase 2 actually converts the pages inplace.
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while
> boarding. Thank you for flying nlogn airlines.
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