| From: | Antonin Houska <ah(at)cybertec(dot)at> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Sehrope Sarkuni <sehrope(at)jackdb(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Joe Conway <mail(at)joeconway(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, "Moon, Insung" <Moon_Insung_i3(at)lab(dot)ntt(dot)co(dot)jp>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS) |
| Date: | 2019-11-11 19:57:35 |
| Message-ID: | 98597.1573502255@antos |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sat, Nov 2, 2019 at 8:23 AM Antonin Houska <ah(at)cybertec(dot)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
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