Re: Offline enabling/disabling of data checksums

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От Andres Freund
Тема Re: Offline enabling/disabling of data checksums
Дата
Msg-id 20190203102109.bnddmgz4axzufipt@alap3.anarazel.de
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Ответ на Re: Offline enabling/disabling of data checksums  (Fabien COELHO <coelho@cri.ensmp.fr>)
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Hi,

On 2019-01-09 07:07:17 +0100, Fabien COELHO wrote:
> There is still no documentation.

Michael, are you planning to address this?  It'd also be useful to state
when you just don't agree with things / don't plan to address them.

Given the docs piece hasn't been addressed, and seems uncontroversial,
I'm marking this patch as returned with feedback. Please resubmit once
ready.


> > > Also, the full page is rewritten... would it make sense to only overwrite
> > > the checksum part itself?
> > 
> > So just writing the page header? I find that a bit scary and don't
> > expect much speedup as the OS would write the whole block anyway I
> > guess? I haven't touched that yet.
> 
> Possibly the OS would write its block size, which is not necessary the same
> as postgres page size?

I think it'd be a bad idea to write more granular. Very commonly that'll
turn a write operation into a read-modify-write (although caching will
often prevent that from being a problem here), and it'll be bad for
flash translation layers.

Greetings,

Andres Freund


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