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Re: SetBufferCommitInfoNeedsSave and race conditions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: SetBufferCommitInfoNeedsSave and race conditions
Date: 2007-06-29 15:13:48
Message-ID: 13140.1183130028@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> On Thu, 2007-06-28 at 20:23 -0400, Tom Lane wrote:
>> The methodology I suggested earlier (involving tracking LSN only at the
>> level of pg_clog pages) isn't going to make that work, unless you
>> somehow force the XID counter forward to the next page boundary.

> If you completely flush WAL after the AccessExclusiveLock has been taken
> by VF, then you are guaranteed to have flushed all asynchronous commits
> that touch the table.

I don't believe this is correct (see system catalogs) and in any case
it's far too fragile for my taste.  I think it'd be a lot better to just
stop referencing the hint bits directly in VACUUM FULL.

			regards, tom lane

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