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Re: Block-level CRC checks

From: Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-30 15:57:33
Message-ID: 4909D96D.8000505@sun.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane napsal(a):
> Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
>> By the way, do you need CRC as a first page member? Is it for future development 
>> like CLOG integration into buffers? Why not put it on the end as and mark it as 
>> a special? It will reduce space requirement when CRC is not enabled.
> 
> ... and make life tremendously more complex for indexes, 

Indexes  uses PageGetSpecial macro and they live with them and PageInit could do 
  correct placement. Only problem are assert macros and extra check which 
verifies correct size of special.

> plus turning
> CRC checking on or off on-the-fly would be problematic.  

Yeah, it is problem.

> I think Alvaro
> has the right idea: just put the field there all the time.

Agree.

	Zdenek



-- 
Zdenek Kotala              Sun Microsystems
Prague, Czech Republic     http://sun.com/postgresql


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