From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PATCHES] Infrastructure changes for recovery (v8)
Date: Mon, 17 Nov 2008 15:51:30 +0200
Message-ID: <492176E2.1000006@enterprisedb.com> (raw)
In-Reply-To: <1223472898.4747.310.camel@ebony.2ndQuadrant>
References: <1222815151.4445.1397.camel@ebony.2ndQuadrant>
<48EC9CC5.6060803@enterprisedb.com>
<1223468660.4747.294.camel@ebony.2ndQuadrant>
<1223472898.4747.310.camel@ebony.2ndQuadrant>
Simon Riggs wrote:
> diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/
> index 063b366..5e64cb4 100644
> --- a/src/backend/access/transam/subtrans.c
> +++ b/src/backend/access/transam/subtrans.c
> @@ -226,6 +226,9 @@ ZeroSUBTRANSPage(int pageno)
> *
> * oldestActiveXID is the oldest XID of any prepared transaction, or nextXid
> * if there are none.
> + *
> + * Note that this is not atomic and is not yet safe to perform while other
> + * processes might access subtrans.
> */
> void
> StartupSUBTRANS(TransactionId oldestActiveXID)
I'm a bit confused by that comment. Does that need to be fixed? It
sounds like it does, because other processes might access subtrans when
StartupSUBTRANS is called, with the patch to allow read-only queries
during recovery. Or is that done in the hot standby patch?
However, I don't see why that isn't safe. StartupSUBTRANS takes the
SubtransControlLock in exclusive mode while it zeroes out subtrans.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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To: pgsql-patches@postgresql.org
Cc: heikki.linnakangas@enterprisedb.com, simon@2ndQuadrant.com, pgsql-hackers@postgresql.org
Subject: Re: [PATCHES] Infrastructure changes for recovery (v8)
In-Reply-To: <492176E2.1000006@enterprisedb.com>
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