Re: Key management with tests

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Kincaid <tomjohnkincaid(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, 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: Key management with tests
Date: 2021-03-18 17:37:43
Message-ID: 20210318173743.GA13514@alvherre.pgsql
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On 2021-Mar-18, Stephen Frost wrote:

> * Alvaro Herrera (alvherre(at)alvh(dot)no-ip(dot)org) wrote:
> > Patch 10 uses the term "WAL-skip relations". What does that mean? Is
> > it "relations that are not WAL-logged"? I suppose we already have a
> > term for this; I'm not sure it's a good idea to invent a different term
> > that is only used in this new place.
> This is discussed in src/backend/access/transam/README, specifically the
> section that talks about Skipping WAL for New RelFileNode. Basically,
> it's the 'wal_level=minimal' optimization which allows WAL to be
> skipped.

Hmm ... that talks about WAL-skipping *changes*, not WAL-skipping
*relations*. I thought WAL-skipping meant unlogged relations, but
I understand now that that's unrelated. In the transam/README, WAL-skip
means a change in a transaction in a relfilenode that, if rolled back,
would disappear; and I'm not sure I understand how the code is handling
the case that a relation is under that condition.

This caught my attention because a comment says "encryption does not
support WAL-skipped relations", but there's no direct change to the
definition of RelFileNodeSkippingWAL() to account for that. Perhaps I
am just overlooking something, since I'm just skimming anyway.

Álvaro Herrera Valdivia, Chile

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