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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Thu, 2 Apr 2026 06:35:59 -0700
Message-ID: 
 <CAKFQuwYcppypeGBwa7ZbDAfoUXSv+kLhJuAXsdwBmKrvy8wDFw@mail.gmail.com>
Subject: Re: pg_get__*_ddl consolidation
To: Japin Li <japinli@hotmail.com>
Cc: Andrew Dunstan <andrew@dunslane.net>,
 Zsolt Parragi <zsolt.parragi@percona.com>,
	Euler Taveira <euler@eulerto.com>,
 =?UTF-8?Q?=C3=81lvaro_Herrera?= <alvherre@kurilemu.de>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Thursday, April 2, 2026, Japin Li <japinli@hotmail.com> wrote:

>
> v3-0004
> =3D=3D=3D=3D=3D=3D=3D=3D
>
> 1.
> +       append_ddl_option(&buf, pretty, 4, "WITH TEMPLATE =3D template0")=
;
>
> I'm curious why WITH TEMPLATE =3D template0 is hardcoded. For example:
>
>   [local]:1374846 postgres=3D# create database db01 IS_TEMPLATE true;
>   CREATE DATABASE
>   [local]:1374846 postgres=3D# create database db02 template db01;
>   CREATE DATABASE
>   [local]:1374846 postgres=3D# select pg_get_database_ddl('db02');
>                                                  pg_get_database_ddl
>   ------------------------------------------------------------
> -----------------------------------------------------
>    CREATE DATABASE db02 WITH TEMPLATE =3D template0 ENCODING =3D 'UTF8'
> LOCALE_PROVIDER =3D libc LOCALE =3D 'en_US.UTF-8';
>    ALTER DATABASE db02 OWNER TO japin;
>   (2 rows)
>
> Is this working as expected?
>
> It seems there's no way to reconstruct the WITH TEMPLATE clause, right?
> A comment here would help.


There is no way or use in constructing the original template clause, though
I agree it=E2=80=99s worth a comment.  At the end of the day the catalog da=
ta that
was found in the db01 database already exists in the db02 database when
executing these DLL reconstruction functions against the existing db02
database.  Taking nothing from the template is the correct behavior - hence
template0.

David J.

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On Thursday, April 2, 2026, Japin Li &lt;<a href=3D"mailto:japinli@hotmail.=
com">japinli@hotmail.com</a>&gt; wrote:<br><blockquote class=3D"gmail_quote=
" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><=
br>v3-0004<br>
=3D=3D=3D=3D=3D=3D=3D=3D<br>
<br>
1.<br>
+=C2=A0 =C2=A0 =C2=A0 =C2=A0append_ddl_option(&amp;buf, pretty, 4, &quot;WI=
TH TEMPLATE =3D template0&quot;);<br>
<br>
I&#39;m curious why WITH TEMPLATE =3D template0 is hardcoded. For example:<=
br>
<br>
=C2=A0 [local]:1374846 postgres=3D# create database db01 IS_TEMPLATE true;<=
br>
=C2=A0 CREATE DATABASE<br>
=C2=A0 [local]:1374846 postgres=3D# create database db02 template db01;<br>
=C2=A0 CREATE DATABASE<br>
=C2=A0 [local]:1374846 postgres=3D# select pg_get_database_ddl(&#39;db02=
9;);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0pg_get_database_ddl<br>
=C2=A0 ------------------------------<wbr>------------------------------<wb=
r>------------------------------<wbr>-----------------------<br>
=C2=A0 =C2=A0CREATE DATABASE db02 WITH TEMPLATE =3D template0 ENCODING =3D =
&#39;UTF8&#39; LOCALE_PROVIDER =3D libc LOCALE =3D &#39;en_US.UTF-8&#39;;<b=
r>
=C2=A0 =C2=A0ALTER DATABASE db02 OWNER TO japin;<br>
=C2=A0 (2 rows)<br>
<br>
Is this working as expected?<br>
<br>
It seems there&#39;s no way to reconstruct the WITH TEMPLATE clause, right?=
<br>
A comment here would help.</blockquote><div><br></div><div>There is no way =
or use in constructing the original template clause, though I agree it=E2=
=80=99s worth a comment.=C2=A0 At the end of the day the catalog data that =
was found in the db01 database already exists in the db02 database when exe=
cuting these DLL reconstruction functions against the existing db02 databas=
e.=C2=A0 Taking nothing from the template is the correct behavior - hence t=
emplate0.</div><div><br></div><div>David J.</div><div><br></div>

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