Re: Block-level CRC checks

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-29 19:56:58
Message-ID: 20081029195658.GL4331@alvh.no-ip.org
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Alvaro Herrera wrote:

> There are some gotchas in this patch:
>
> 1. it does not consider hint bits other than the ones defined in htup.h.
> Some index AMs use hint bits to "kill" tuples (LP_DEAD mostly, I think).
> This means that CRCs will be broken for such pages when pages are torn.

The "other hint bits" are:

- LP_DEAD as used by the various callers of ItemIdMarkDead.
- PD_PAGE_FULL
- BTPageOpaque->btpo_flags and btpo_cycleid

All of them are changed with only SetBufferCommitInfoNeedsSave being
called afterwards.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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