Re: storing an explicit nonce

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Neil Chen <carpenter(dot)nail(dot)cz(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Kincaid <tomjohnkincaid(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>
Subject: Re: storing an explicit nonce
Date: 2021-05-27 15:12:17
Message-ID: 20210527151217.GD5646@momjian.us
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On Thu, May 27, 2021 at 05:45:21PM +0800, Neil Chen wrote:
> Greetings,
>
> On Thu, May 27, 2021 at 4:52 PM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> >
> > I am confused why checksums, which are widely used, acceptably require
> > wal_log_hints, but there is concern that file encryption, which is
> > heavier, cannot acceptably require wal_log_hints.  I must be missing
> > something.
> >
> > Why can't checksums also throw away hint bit changes like you want to do
> > for file encryption and not require wal_log_hints?
>
>
>
> I'm really confused about it, too. I read the above communication, not sure if
> my understanding is correct... What we are facing is not only the change of
> flag such as *pd_flags*, but also others like pointer array changes in btree
> like Robert said. We don't need them to write a WAL record.

Well, the code now does write full page images for hint bit changes, so
it should work fine.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

If only the physical world exists, free will is an illusion.

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