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In-Reply-To: <37eaba89-baeb-4087-b8ec-3bd8f1f1a8db@pgbackrest.org>
From: Corey Huinker <corey.huinker@gmail.com>
Date: Thu, 19 Mar 2026 00:20:40 -0400
Message-ID: 
 <CADkLM=dFzTfctUfX6Gvmyx-DB2KyEqeviCVajUx4onw6PNarfw@mail.gmail.com>
Subject: Re: Return pg_control from pg_backup_stop().
To: David Steele <david@pgbackrest.org>
Cc: Michael Paquier <michael@paquier.xyz>, Haibo Yan <tristan.yim@gmail.com>,
	Pg Hackers <pgsql-hackers@postgresql.org>,
 Heikki Linnakangas <hlinnaka@iki.fi>,
	Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
	Fujii Masao <masao.fujii@gmail.com>
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On Wed, Mar 18, 2026 at 10:56=E2=80=AFPM David Steele <david@pgbackrest.org=
> wrote:

> Hi Corey,
>
> On 3/19/26 04:00, Corey Huinker wrote:
> >     Whatever gets committed for PG19 I'll write a followup patch to
> >     describe
> >     the hazards of reading pg_control and generally how to get a good
> copy.
> >     However, this will be complicated enough that the best answer will
> >     likely be to use pg_basebackup or some other reputable backup
> software.
> >     I don't love this -- I feel like the low-level interface should be
> >     usable with such hazards.
> >
> > Surya Poondla and I had decided on this patchset as a pair-reviewing
> > exercise. However, events have overtaken us, and several other people
> > have chimed in expressing the same concerns that we had observed but
> > hadn't yet completed our review.
>
> Thank you both for having a look!
>
>  > All of the main concerns that we had > found up to this point have
> been addressed in the lastest patchset,
> > except for the trivial observation that the ereport() uses the old styl=
e
> > and doesn't need the set of parens around (errmsg(), errhint()).
>
> Grep shows there are lots of messages with the new style but many more
> in the old style. Presumably they are only being updated as they are
> modified.


That's always been my assumption. Not worth the churn.


> Do you happen to know the commit or message thread where this
> policy was started? I've been searching but it is such a generic search
> term.
>

I limited my git log -p to elog.h, and it seems it started with
e3a87b4991cc back in 2020. The only reason I knew about it was that I used
to do backports from v13 to unsupported versions, and the new style would
cause the build to fail on an otherwise clean cherry pick.


> It seems to me you've still done a review. Confirming what the other
> reviewers found is good info to have.
>

Of a sort, yes, but our review doesn't touch the "is this a good idea"
question, which has been by far the thing most in need of reviewing across
the long discussion threads.

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Mar 18,=
 2026 at 10:56=E2=80=AFPM David Steele &lt;<a href=3D"mailto:david@pgbackre=
st.org">david@pgbackrest.org</a>&gt; wrote:<br></div><blockquote class=3D"g=
mail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204=
,204,204);padding-left:1ex">Hi Corey,<br>
<br>
On 3/19/26 04:00, Corey Huinker wrote:<br>
&gt;=C2=A0 =C2=A0 =C2=A0Whatever gets committed for PG19 I&#39;ll write a f=
ollowup patch to<br>
&gt;=C2=A0 =C2=A0 =C2=A0describe<br>
&gt;=C2=A0 =C2=A0 =C2=A0the hazards of reading pg_control and generally how=
 to get a good copy.<br>
&gt;=C2=A0 =C2=A0 =C2=A0However, this will be complicated enough that the b=
est answer will<br>
&gt;=C2=A0 =C2=A0 =C2=A0likely be to use pg_basebackup or some other reputa=
ble backup software.<br>
&gt;=C2=A0 =C2=A0 =C2=A0I don&#39;t love this -- I feel like the low-level =
interface should be<br>
&gt;=C2=A0 =C2=A0 =C2=A0usable with such hazards.<br>
&gt; <br>
&gt; Surya Poondla and I had decided on this patchset as a pair-reviewing <=
br>
&gt; exercise. However, events have overtaken us, and several other people =
<br>
&gt; have chimed in expressing the same concerns that we had observed but <=
br>
&gt; hadn&#39;t yet completed our review. <br>
<br>
Thank you both for having a look!<br>
<br>
=C2=A0&gt; All of the main concerns that we had &gt; found up to this point=
 have <br>
been addressed in the lastest patchset,<br>
&gt; except for the trivial observation that the ereport() uses the old sty=
le <br>
&gt; and doesn&#39;t need the set of parens around (errmsg(), errhint()). <=
br>
<br>
Grep shows there are lots of messages with the new style but many more <br>
in the old style. Presumably they are only being updated as they are <br>
modified.</blockquote><div><br></div><div>That&#39;s always been my assumpt=
ion. Not worth the churn.</div><div></div><div>=C2=A0</div><blockquote clas=
s=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid r=
gb(204,204,204);padding-left:1ex"> Do you happen to know the commit or mess=
age thread where this <br>
policy was started? I&#39;ve been searching but it is such a generic search=
 <br>
term.<br></blockquote><div></div><div><br></div><div>I limited my git log -=
p to elog.h, and it seems it started with e3a87b4991cc back in 2020. The on=
ly reason I knew about it was that I used to do backports from v13 to unsup=
ported versions, and the new style would cause the build to fail on an othe=
rwise clean cherry pick.</div><div></div><div>=C2=A0</div><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex">
It seems to me you&#39;ve still done a review. Confirming what the other <b=
r>
reviewers found is good info to have.<br></blockquote><div><br></div>Of a s=
ort, yes, but our review doesn&#39;t touch the &quot;is this a good idea&qu=
ot; question, which has been by far the thing most in need of reviewing acr=
oss the long discussion threads.</div></div>

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