Re: [HACKERS] wal_checksum = on (default) | off

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] wal_checksum = on (default) | off
Date: 2007-01-05 14:39:53
Message-ID: 15436.1168007993@sss.pgh.pa.us
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"Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at> writes:
> Ok, so when you need CRC's on a replicate (but not on the master) you
> turn it
> off during standby replay, but turn it on when you start the replicate
> for normal operation.

Thought: even when it's off, the CRC had better be computed for
shutdown-checkpoint records. Else there's no way to turn it on even
with a postmaster restart --- unless we accept the idea of poking a hole
in the normal mode. (Which I still dislike, and even more so if the
special value is zero. Almost any other value would be safer than zero.)

On the whole, though, I still don't want to put this in. I don't think
Simon has thought it through sufficiently, and we haven't even seen any
demonstration of a big speedup.

(Another hole in the implementation as given: pg_resetxlog.)

regards, tom lane

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