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From: Pavel Stehule <pavel.stehule@gmail.com>
Date: Thu, 2 Apr 2026 20:57:41 +0200
Message-ID: 
 <CAFj8pRDDDhEVvQg82+f-X9DXgi8iwXPXR0s+m4oDR+x9+1peog@mail.gmail.com>
Subject: Re: WIP - xmlvalidate implementation from TODO list
To: Marcos Magueta <maguetamarcos@gmail.com>
Cc: Jim Jones <jim.jones@uni-muenster.de>,
 Andrey Borodin <x4mmm@yandex-team.ru>,
	Kirill Reshke <reshkekirill@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Hi

=C4=8Dt 2. 4. 2026 v 20:22 odes=C3=ADlatel Marcos Magueta <maguetamarcos@gm=
ail.com>
napsal:

> Hey Jim and Pavel, thanks for demonstrating interest.
>
> > XML is a little bit outdated - but the proposed infrastructure can be
> used for any documents, so it can theoretically supports json, jsonb too
> [...]. I expect something like XMLVALIDATE will be JSON standard in a few
> years.
>
> That doesn't sound like a bad idea to me. But I suspect I would need to
> almost completely revamp the implementation in the patch so far, so I wou=
ld
> like to confirm a few things before committing to anything on that front.
>

It is usual when you design a feature that is not fully described by
standard :-/. And then it is good to start primary from part (command),
that is well described by standard.


>
> I am still unsure how the permissions would be managed properly with the
> API approach. It seems to me we could rely on the ACL like before, but I
> sense there's something more arcane around it when it comes to the
> extension.
>

There are two different things - 1. possibility to registrate xml schema -
you need just to CREATE right for related pg_namespace, 2. possibility to
use xml schema - and you need to USAGE right - and this can be checked
inside extension. Probably you cannot use all ACL related macros, and maybe
you have to design some function instead of GRANT and REVOKE.  Maybe some
form of RLS can be used. When you separate storage of XML schemas to an
extension, then you can implement just some minimalistic implementation
(just what is necessary for regress tests) - and some more complex storage
of XML schema can be designed (developed) outside the main branch.
Hypothetical storage from contrib can be enhanced step by step.

Regards

Pavel


> I didn't realize, but DB2 actually gives you decomposition over an xml
> hierarchy into tables, which is an insanely valuable feature. I wonder ho=
w
> we could go with that here using the current catalog approach.
>
> Is there anything else that might be troublesome with changing approaches=
?
>
> Regards, Marcos.
>

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<div dir=3D"ltr"><div>Hi</div><br><div class=3D"gmail_quote gmail_quote_con=
tainer"><div dir=3D"ltr" class=3D"gmail_attr">=C4=8Dt 2. 4. 2026 v=C2=A020:=
22 odes=C3=ADlatel Marcos Magueta &lt;<a href=3D"mailto:maguetamarcos@gmail=
.com">maguetamarcos@gmail.com</a>&gt; napsal:<br></div><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2=
04,204,204);padding-left:1ex"><div dir=3D"ltr"><div><div>Hey Jim and Pavel,=
 thanks for demonstrating interest.<br><br>&gt;=C2=A0XML is a little bit ou=
tdated=C2=A0- but the proposed infrastructure=C2=A0can be used for any docu=
ments, so it can theoretically supports json, jsonb too [...]. I expect som=
ething like XMLVALIDATE will be JSON standard in a few years.<br><br>That d=
oesn&#39;t sound like a bad idea to me. But I suspect I would need to almos=
t completely revamp the implementation in the patch so far, so I would like=
 to confirm a few things before committing to anything on that front.<br></=
div></div></div></blockquote><div><br></div><div>It is usual when you desig=
n a feature that is not fully described by standard :-/. And then it is goo=
d to start primary from part (command), that is well described by standard.=
</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0p=
x 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><d=
iv dir=3D"ltr"><div><div><br></div>I am still unsure how the permissions wo=
uld be managed properly with the API approach. It seems to me we could rely=
 on the ACL like before, but I sense there&#39;s something more arcane arou=
nd it when it comes to the extension.</div></div></blockquote><div><br></di=
v><div>There are two different things - 1. possibility to registrate xml sc=
hema - you need just to CREATE right for related pg_namespace, 2. possibili=
ty to use xml schema - and you need to USAGE right - and this can be checke=
d inside extension. Probably you cannot use all ACL related macros, and may=
be you have to design some function instead of GRANT and REVOKE.=C2=A0 Mayb=
e some form of RLS can be used. When you separate storage of XML schemas to=
 an extension, then you can implement just some minimalistic implementation=
 (just what is necessary for regress tests) - and some more complex storage=
 of XML schema can be designed (developed) outside the main branch. Hypothe=
tical storage from contrib can be enhanced step by step.=C2=A0</div><div><b=
r></div><div>Regards</div><div><br></div><div>Pavel</div><div><br></div><di=
v><br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0=
.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"l=
tr"><div><br>I didn&#39;t realize, but DB2 actually gives you decomposition=
 over an xml hierarchy into tables, which is an insanely valuable feature. =
I wonder how we could go with that here using the current catalog approach.=
<br><br></div><div>Is there anything else that might be troublesome with ch=
anging approaches?</div><div><br></div>Regards, Marcos.</div>
</blockquote></div></div>

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