From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: unlogged tables vs. GIST |
Date: | 2010-12-17 19:33:28 |
Message-ID: | AANLkTikN5D=3RGzS_YSm3k2_5VchRzR2vCquuTE4zbUS@mail.gmail.com |
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On Fri, Dec 17, 2010 at 2:31 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> Another possibly-useful thing about mandating a full page header for
>> every page is that it might give us a way of avoiding unnecessary full
>> page writes. As I wrote previously:
>
> Could we do that via a bufmgr status bit, instead? Heikki's idea has
> the merit that it actually reduces bufmgr's knowledge of page headers,
> rather than increasing it (since a buffer marked UNLOGGED would need
> no assumptions at all about its content).
That was my first thought, but it doesn't work. The buffer could be
evicted from shared_buffers and read back in. If a checkpoint
intervenes meanwhile, we're OK, but otherwise you fail to emit an
otherwise-needed FPI.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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