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In-Reply-To: <68a012d3-121b-418a-913b-aa0aaf32915d@uni-muenster.de>
From: Marcos Magueta <maguetamarcos@gmail.com>
Date: Tue, 6 Jan 2026 15:03:15 -0300
Message-ID: <CAN3aFCcXwS7BrU1gHRUEBH3G59EVf_7LUhLeEWqW2Sc9Vk5k-A@mail.gmail.com>
Subject: Re: WIP - xmlvalidate implementation from TODO list
To: Jim Jones <jim.jones@uni-muenster.de>
Cc: Andrey Borodin <x4mmm@yandex-team.ru>, Kirill Reshke <reshkekirill@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Hey Jim!

On 06.01.26, Jim Jones <jim.jones@uni-muenster.de> wrote:
> The result of <XML validate> is R.
That was an oversight on my behalf, I had a hard time understanding the
standard, but now the validation of DOCUMENT and CONTENT being accepted
makes more sense.

The current patch has some issues.

>  xmloption is document_or_content. But xmlvalidate_text_schema() always
validates as a document.
As Andrey noticed, we should indeed support both a document and content.
Which entails into an iterative validation (for each node provided) on
content mode, so I should likely add the xmloption back. The fact it worked
with the example I created was actually luck.

Also, I am not sure if some variables used inside of the PG_TRY are memory
safe -- notice that none right now is set to volatile, despite being
accessed in different parts of the block; other functions in xml.c do
handle such correctly it seems (like xml_parse).

About the syntax proposal by Jim, I have no problems with complying to it.
It does increase considerably the scope from what I originally intended,
but that's the price to have something actually nice.

I can think of several useful extensions we could consider in a further
implementation:

Schema Dependencies/Imports
CREATE XMLSCHEMA base AS '...';
CREATE XMLSCHEMA extended
  IMPORTS base
  AS '...';

Schema Versioning
CREATE XMLSCHEMA patient VERSION '1.0' AS '...';
CREATE XMLSCHEMA patient VERSION '2.0' AS '...';
XMLVALIDATE(doc ACCORDING TO XMLSCHEMA patient VERSION '2.0')

Custom Error Messages
CREATE XMLSCHEMA patient
  AS '...'
  ERROR MESSAGE 'Patient record does not match schema v2.0';

Schema inference from samples (if the lib supports it, that is)
CREATE XMLSCHEMA patient
    INFER FROM (SELECT data FROM patient_samples);

And much more, but perhaps that's already too ambitious for a first version.

I'll wait for the others to ring their bells.

Regards, Magueta.

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<div dir=3D"ltr"><div>Hey Jim!</div><br><div class=3D"gmail_quote gmail_quo=
te_container"><div dir=3D"ltr" class=3D"gmail_attr">On 06.01.26, Jim Jones =
&lt;<a href=3D"mailto:jim.jones@uni-muenster.de">jim.jones@uni-muenster.de<=
/a>&gt; wrote:</div><div dir=3D"ltr" class=3D"gmail_attr">&gt; The result o=
f &lt;XML validate&gt; is R.</div><div class=3D"gmail_attr">That was an ove=
rsight on=C2=A0my behalf, I had a hard time understanding the standard, but=
 now the validation of DOCUMENT and CONTENT being accepted makes more sense=
.</div><div class=3D"gmail_attr"><br></div><div class=3D"gmail_attr">The cu=
rrent patch has some issues.</div><div class=3D"gmail_attr"><br></div><div =
class=3D"gmail_attr">&gt;=C2=A0
xmloption is document_or_content. But xmlvalidate_text_schema() always=20
validates as a document.</div><div class=3D"gmail_attr">As Andrey noticed, =
we should indeed support both a document and content. Which entails into an=
 iterative validation (for each node provided) on content mode, so I should=
 likely add the xmloption back. The fact it worked with the example I creat=
ed was actually luck.<br><br>Also, I am not sure if some variables used ins=
ide of the PG_TRY are memory safe -- notice that none right now is set to v=
olatile, despite being accessed in different parts of the block; other func=
tions in xml.c do handle such correctly it seems (like xml_parse).<br><br><=
/div><div class=3D"gmail_attr">About the syntax proposal by Jim, I have no =
problems with complying to it. It does increase considerably the scope from=
 what I originally intended, but that&#39;s the price to have something act=
ually nice.<br><br></div><div class=3D"gmail_attr">I can think of several u=
seful extensions we could consider in a further implementation:<br><br>Sche=
ma Dependencies/Imports<br>CREATE XMLSCHEMA base AS &#39;...&#39;;<br>CREAT=
E XMLSCHEMA extended<br>=C2=A0 IMPORTS base<br>=C2=A0 AS &#39;...&#39;;<br>=
<br>Schema Versioning<br>CREATE XMLSCHEMA patient VERSION &#39;1.0&#39; AS =
&#39;...&#39;;<br>CREATE XMLSCHEMA patient VERSION &#39;2.0&#39; AS &#39;..=
.&#39;;<br>XMLVALIDATE(doc ACCORDING TO XMLSCHEMA patient VERSION &#39;2.0&=
#39;)<br><br>Custom Error Messages<br>CREATE XMLSCHEMA patient<br>=C2=A0 AS=
 &#39;...&#39;<br>=C2=A0 ERROR MESSAGE &#39;Patient record does not match s=
chema v2.0&#39;;<br><br>Schema inference from samples (if the lib supports =
it, that is)<br>CREATE XMLSCHEMA patient<br>=C2=A0 =C2=A0 INFER FROM (SELEC=
T data FROM patient_samples);<br><br></div><div class=3D"gmail_attr">And mu=
ch more, but perhaps that&#39;s already too ambitious for a first version.<=
br><br></div><div class=3D"gmail_attr">I&#39;ll wait for the others to ring=
 their bells.<br><br></div><div class=3D"gmail_attr">Regards, Magueta.</div=
></div></div>

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