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Re: crash-safe visibility map, take three

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: crash-safe visibility map, take three
Date: 2010-11-30 16:40:10
Message-ID: 27743.1291135210@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> That's definitely sucky, but in some ways it would be more complicated
> if they did, because I don't think all-visible on the master implies
> all-visible on the standby.

Ouch.  That seems like it could shoot down all these proposals.  There
definitely isn't any way to make VM crash-safe if there is no WAL-driven
mechanism for setting the bits.

I guess what we need is a way to delay the application of such a WAL
record on the slave until it's safe, which means the record also has to
carry some indication of the youngest XMIN on the page.

			regards, tom lane

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Subject: Re: crash-safe visibility map, take three
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