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Re: crash-safe visibility map, take three

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: crash-safe visibility map, take three
Date: 2010-11-30 15:38:02
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Lists: pgsql-hackers
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 30.11.2010 06:57, Robert Haas wrote:
>> I can't say I'm totally in love with any of these designs.  Anyone
>> else have any ideas, or any opinions about which one is best?

> Well, the design I've been pondering goes like this:

Wouldn't it be easier and more robust to just consider VM bit changes to
be part of the WAL-logged actions?  That would include updating LSNs on
VM pages and flushing VM pages to disk during checkpoint based on their
LSN values.  All of these other schemes seem too complicated and not
provably correct.

Of course, that'd mean doing the bit changes inside the critical
sections for the related actions, so it's not a trivial change
code-wise, but neither are these other ideas.

			regards, tom lane

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