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From: Jim Jones <[email protected]>
To: Pavel Stehule <[email protected]>
Cc: Marcos Magueta <[email protected]>
Cc: Andrey Borodin <[email protected]>
Cc: Kirill Reshke <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: WIP - xmlvalidate implementation from TODO list
Date: Tue, 31 Mar 2026 11:29:38 +0200
Message-ID: <[email protected]> (raw)
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On 30/03/2026 22:28, Pavel Stehule wrote:
> I checked db2 doc, and if I understand their doc, the XML schema is
> identified by "relational identifier" SQLschema.name
> 
> So taking XML schema as catalog object is the correct analogy and using
> acl looks to me correct.

+1

> But what is different (patch and db2), one relational identifier can
> identify a group of XML schemas. So there is relation 1:N not 1:1. You
> can see the REGISTER XMLSCHEMA command.

I wonder what are the applications for this 1:N relationship between xml
schemas and their identifiers. Sounds cool though.

> The schema registration is different on MSSQL where it is more similar
> to some local cache, and schema is identified only by uri. In this case
> using ACL can be messy, and I can imagine having some dedicated role
> that can register a new xml schema. But MSSQL doesn't support SQL/XML
> XMLVALIDATE function.
> 
> Both concepts are workable, and I have no strong preference for one or
> second (maybe DB2 concept is better for Postgres, probably DB2 concept
> is closer to SQL/XML). But if we use relational identifiers, then it
> should be consistent with other usage of relational identifiers - there
> ACL should be used.


A few other things I noticed in v6

== event triggers (event_trigger.c) ==

OBJECT_XMLSCHEMA is in the elog(ERROR) path of stringify_grant_objtype()
and stringify_adefprivs_objtype(). Since the grammar does support
GRANT/REVOKE ... ON XMLSCHEMA, any event trigger on ddl_command_end that
fires during a GRANT on an XML schema will raise a elog(ERROR,
"unsupported object type").

An additional test here would be nice as well.

== corrupt dump ==

pg_dump is ignoring GRANT statements. Since the feature supports
GRANT/REVOKE on XMLSCHEMAS, omitting ACL dump means privileges are
silently lost during dump/restore.

== inconsistent DDL statements ==

The docs suggest that ALTER XMLSCHEMA ... IF EXISTS is supported, which
isn't the case. It should be either implemented or just removed from the
docs.

== different error message for build without libxml ==

In xml.c the error messag used is "unsupported XML feature", but you're
using "xmlschema support requires libxml" in pg_xmlschema.c. I think we
should be consistent here.

Thanks!

Best, Jim








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