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References: <CAM_eQjzTLtt1X9WKvMV6Rew0UvxT3mmhimZa9WT-vqaPjmXk-g@mail.gmail.com>
In-Reply-To: <CAM_eQjzTLtt1X9WKvMV6Rew0UvxT3mmhimZa9WT-vqaPjmXk-g@mail.gmail.com>
From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Tue, 27 Jan 2026 09:51:58 -0700
Message-ID: <CAKFQuwbHpDVQt0=nfC7To=AxAkDs6fmvv-40Qcw6z=VtW23GEQ@mail.gmail.com>
Subject: Re: docs: warn about post-data-only schema dumps with parallel restore.
To: vaibhave postgres <postgresvaibhave@gmail.com>
Cc: pgsql-hackers@postgresql.org
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On Sun, Jan 25, 2026 at 10:23=E2=80=AFPM vaibhave postgres <
postgresvaibhave@gmail.com> wrote:

> Hi hackers,
>
> Following up on the discussion in [1] about pg_restore failing to restore
> post-data items due to circular foreign key deadlocks.
>
> I=E2=80=99m attaching a doc patch that adds a warning about using post-da=
ta-only
> schema dumps together with parallel restore.
>
> Thanks.
>
> [1] Re: pg_restore: fails to restore post-data items due to circular FK
> deadlock - Mailing list pgsql-bugs : Postgres Professional
> <https://postgrespro.com/list/id/3908.1717093769@sss.pgh.pa.us>
>

The note element would align with the sibling para element.

Not a fan of the patch overall though.  I'd want to add something to
pg_restore noting that use of --jobs for constraint restoration needs
schema information to compute the restoration order.

There is also just a lot of detail here when something like:

<para>Consider always combining pre-data and post-data in the same command
so that parallel restores have the necessary dependency information to
create constraints in parallel.</para>

Any other content related to this probably belongs in the Notes section.

David J.

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<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_defa=
ult" style=3D"font-family:arial,helvetica,sans-serif"><span style=3D"font-f=
amily:Arial,Helvetica,sans-serif">On Sun, Jan 25, 2026 at 10:23=E2=80=AFPM =
vaibhave postgres &lt;<a href=3D"mailto:postgresvaibhave@gmail.com" target=
=3D"_blank">postgresvaibhave@gmail.com</a>&gt; wrote:</span></div></div><di=
v class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><=
div dir=3D"ltr">Hi hackers,<div><br></div><div>Following up on the discussi=
on in [1] about pg_restore failing to restore post-data items due to circul=
ar foreign key deadlocks.=C2=A0=C2=A0</div><div><br></div><div>I=E2=80=99m =
attaching a doc patch that adds a warning about using post-data-only schema=
 dumps together with parallel restore.</div><div><br></div><div>Thanks.</di=
v><div><br></div><div>[1]=C2=A0<a href=3D"https://postgrespro.com/list/id/3=
908.1717093769@sss.pgh.pa.us" target=3D"_blank">Re: pg_restore: fails to re=
store post-data items due to circular FK deadlock - Mailing list pgsql-bugs=
 : Postgres Professional</a></div></div></blockquote><div><br></div><div><d=
iv class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"=
>The note element would align with the sibling para element.</div><div clas=
s=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><br></=
div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-=
serif">Not a fan of the patch overall though.=C2=A0 I&#39;d want to add som=
ething to pg_restore noting that use of --jobs for constraint restoration n=
eeds schema information to compute the restoration order.</div><div class=
=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><br></d=
iv><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-s=
erif">There is also just a lot of detail here when something like:</div><di=
v class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif">=
<br></div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica=
,sans-serif">&lt;para&gt;Consider always combining pre-data and post-data i=
n the same command so that parallel=C2=A0restores have the necessary depend=
ency information to create constraints in parallel.&lt;/para&gt;</div><div =
class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><b=
r></div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,s=
ans-serif">Any other content related to this probably belongs in the Notes =
section.</div><div class=3D"gmail_default" style=3D"font-family:arial,helve=
tica,sans-serif"><br></div><div class=3D"gmail_default" style=3D"font-famil=
y:arial,helvetica,sans-serif">David J.</div><div class=3D"gmail_default" st=
yle=3D"font-family:arial,helvetica,sans-serif"><br></div></div></div></div>
</div>

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