Re: Hard limit on WAL space used (because PANIC sucks)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)heroku(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>
Subject: Re: Hard limit on WAL space used (because PANIC sucks)
Date: 2013-06-07 16:59:42
Message-ID: 25149.1370624382@sss.pgh.pa.us
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Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> writes:
> On 07.06.2013 19:33, Tom Lane wrote:
>> Not only is that a horrible layering/modularity violation, but surely
>> LockBuffer can have no idea how much WAL space will be needed.

> It can be just a conservative guess, like, 32KB. That should be enough
> for almost all WAL-logged operations. The only exception that comes to
> mind is a commit record, which can be arbitrarily large, when you have a
> lot of subtransactions or dropped/created relations.

What happens when several updates are occurring concurrently?

regards, tom lane

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