Re: COMMIT NOWAIT Performance Option

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
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 19:12:24
Message-ID: 200702281912.l1SJCON22868@momjian.us
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Jonah H. Harris wrote:
> 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.

Am am not comfortable starting and having something fail later. How
other databases do it is not an issue for me.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com

+ If your life is a hard drive, Christ can be your backup. +

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