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From: Alvaro Herrera <[email protected]>
To: Simon Riggs <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: FOR SHARE vs FOR UPDATE locks
Date: Fri, 1 Dec 2006 08:37:11 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

Simon Riggs wrote:

> ISTM that multitrans could be used here. Two xids, one xmax.

Hmm, yeah, this seems a reasonable suggestion.  The problem is that we
don't have a mechanism today for saying "this Xid holds a shared lock,
this one holds an exclusive lock".  So code-wise it wouldn't be simple
to do.  It's a single bit per Xid, but I don't see where to store such a
thing.

I'm not sure we can use the simple "raise an ERROR" answer though,
because for users that would be a regression.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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