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: | 2010-12-14 22:14:28 |
Message-ID: | AANLkTing6fW66mdmwu3CKLEDOKZ+WQ-wNsiPFoXNwV==@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Dec 14, 2010 at 4:55 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Tue, Dec 14, 2010 at 4:24 PM, Heikki Linnakangas
>> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>>> Hmm, the first idea that comes to mind is to use a counter like the
>>> GetXLogRecPtrForTemp() counter I used for temp tables, but global, in shared
>>> memory. However, that's a bit problematic because if we store a value from
>>> that counter to LSN, it's possible that the counter overtakes the XLOG
>>> insert location, and you start to get xlog flush errors. We could avoid that
>>> if we added a new field to the GiST page header, and used that to store the
>>> value in the parent page instead of the LSN.
>
>> That doesn't seem ideal, either, because now you're eating up some
>> number of bytes per page in every GIST index just on the off chance
>> that one of them is unlogged.
>
> On-disk compatibility seems problematic here as well.
Good point.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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