Re: Online verification of checksums

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Banck <michael(dot)banck(at)credativ(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Online verification of checksums
Date: 2019-03-18 06:05:59
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On Mon, Mar 18, 2019 at 01:43:08AM -0400, Stephen Frost wrote:
> To be clear, I agree completely that we don't want to be reporting false
> positives or "this might mean corruption!" to users running the tool,
> but I haven't seen a good explaination of why this needs to involve the
> server to avoid that happening. If someone would like to point that out
> to me, I'd be happy to go read about it and try to understand.

The mentions on this thread that the server has all the facility in
place to properly lock a buffer and make sure that a partial read
*never* happens and that we *never* have any kind of false positives,
directly preventing the set of issues we are trying to implement
workarounds for in a frontend tool are rather good arguments in my
opinion (you can grep for BufferDescriptorGetIOLock() on this thread
for example).

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