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Re: Block-level CRC checks

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Brian Hurt <bhurt(at)janestcapital(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-02 13:57:56
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> Brian Hurt wrote:
>> Another possibility is to just not checksum the hint bits...

> That would work. But I'm afraid it'd make the implementation a lot more 
> invasive, and also slower. The buffer manager would have to know what 
> kind of a page it's dealing with, heap or index or FSM or what, to know 
> where the hint bits are. Then it would have to follow the line pointers 
> to locate the hint bits, and mask them out for the CRC calculation.

Right.  The odds are that this'd actually be slower than the
double-buffer method, because of all the added complexity.  And it would
really suck from a modularity standpoint to have bufmgr know about all

The problem we still have to solve is torn pages when writing back a
hint-bit update ...

			regards, tom lane

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