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From: Alvaro Herrera <[email protected]>
To: Stephen Frost <[email protected]>
Cc: Bruce Momjian <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Cc: Tom Kincaid <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Subject: Re: Key management with tests
Date: Thu, 18 Mar 2021 14:37:43 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 2021-Mar-18, Stephen Frost wrote:

> * Alvaro Herrera ([email protected]) 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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