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Re: Moving more work outside WALInsertLock

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Moving more work outside WALInsertLock
Date: 2011-12-15 16:32:47
Message-ID: CAMkU=1zT2NOoug6oWZ0tRvkVM74OBzw_GM+ebyRC68nsF1ZM9Q@mail.gmail.com (view raw or flat)
Thread:
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On Thu, Dec 15, 2011 at 7:34 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>> I've been experimenting with different approaches to do that, but one
>> thing is common among all of them: you need to know the total amount of
>> WAL space needed for the record, including backup blocks, before you
>> take the lock. So, here's a patch to move things around in XLogInsert()
>> a bit, to accomplish that.
>
> This patch may or may not be useful, but this description of it is utter
> nonsense, because we already do compute that before taking the lock.
> Please try again to explain what you're doing?

Currently the CRC of all the data minus the header is computed outside the lock,
but then the header's computation is added and the CRC is finalized
inside the lock.


Cheers,

Jeff

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