Horton

Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS)

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Bruce Momjian <bruce@momjian.us>, Sehrope Sarkuni <sehrope@jackdb.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Joe Conway <mail@joeconway.com>, Stephen Frost <sfrost@snowman.net>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, "Moon, Insung" <Moon_Insung_i3@lab.ntt.co.jp>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-11-11T19:57:35Z
Lists: pgsql-hackers

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  1. Revamp the WAL record format.

Robert Haas <robertmhaas@gmail.com> wrote:

> On Sat, Nov 2, 2019 at 8:23 AM Antonin Houska <ah@cybertec.at> wrote:
> > Change to hint bits does not result in LSN change in the case I described here
> >
> > https://www.postgresql.org/message-id/28452.1572443058%40antos
> >
> > but I consider this a bug (BTW, I discovered this problem when thinking about
> > the use of LSN as encryption IV). Do you mean any other case? If LSN does not
> > get changed, then the related full-page image WAL record is not guaranteed to
> > be on disk during crash recovery. Thus if page checksum is invalid due to
> > torn-page write, there's now WAL record to fix the page.
> 
> I thought the idea was that the first change to hint bits after a
> given checkpoint produced an FPI, but subsequent changes within the
> same checkpoint cycle do not.

Got it, this is what happens in XLogSaveBufferForHint().

Perhaps we can fix it by issuing XLOG_NOOP record in the cases that produce no
FPI. Of course only if the encryption is enabled.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com