Re: Interesting glitch in autovacuum

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Interesting glitch in autovacuum
Date: 2008-09-10 19:54:23
Message-ID: 1221076463.3913.748.camel@ebony.2ndQuadrant
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On Wed, 2008-09-10 at 11:52 -0400, Tom Lane wrote:

> I'm thinking that maybe an appropriate fix is to insert a
> GetTransactionSnapshot call at the beginning of InitPostgres'
> transaction, thus ensuring that every backend has some vaguely sane
> value for RecentGlobalXmin before it tries to do any database access.

Can't we just set RecentGlobalXmin without getting a Snapshot? There's
no need for a snapshot at that point is there? Just lock ProcArrayLock,
read GlobalXmin, drop lock.

--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support

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