From: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
---|---|
To: | "Bruce Momjian" <bruce(at)momjian(dot)us> |
Cc: | "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Josh Berkus" <josh(at)agliodbs(dot)com>, "Jeff Davis" <pgsql(at)j-davis(dot)com>, pgsql-hackers(at)postgresql(dot)org, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com> |
Subject: | Re: COMMIT NOWAIT Performance Option |
Date: | 2007-02-28 19:10:11 |
Message-ID: | 36e682920702281110o287aae37i69d1e0bdfc97495f@mail.gmail.com |
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Lists: | pgsql-hackers |
On 2/28/07, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > But if the system was shut down uncleanly as the result of a Postgres crash or
> > fast shutdown of Postgres then that isn't an issue. And many users may prefer
> > to bring the system up as soon as possible as long as they know any corrupt
> > pages will be spotted and throw errors as soon as it's seen.
>
> I don't think we should start up a system and only detect the errors
> later.
Which is, of course, how everyone else does it. On block access, the
checksum is verified (if you've turned checksum checking on). I
*really* doubt you want to pull in every page in the database at
startup time to verify the checksum or sequence. Even pages from the
last checkpoint would be a killer.
All of the databases (Oracle, SQL Server, DB2) have a way to perform a
database corruption check which does go out and verify all checksums.
If consistency is stored at the block-level, which is pretty much the
only way to avoid full page writes, you have to accept some level of
possible corruption.
--
Jonah H. Harris, Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
33 Wood Ave S, 3rd Floor | jharris(at)enterprisedb(dot)com
Iselin, New Jersey 08830 | http://www.enterprisedb.com/
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