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commit    8bf257aebac12791dc78a599e4f7dc225893d45e
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Fri Jun 12 01:25:45 2026 +0000

    Fix handling of namespace nodes in xpath() (xml)
    
    xpath() attempted to call xmlCopyNode() and xmlNodeDump() on a
    XML_NAMESPACE_DECL, finishing with a confusing error:
    =# SELECT xpath('//namespace::foo', '<root xmlns:foo="http://127.0.0.1"/>');
    ERROR:  53200: could not copy node
    CONTEXT:  SQL function "xpath" statement 1
    
    xpath() is changed so as it goes through xmlXPathCastNodeToString()
    instead, that is able to handle namespace nodes.  xml2 uses the same
    solution.  This issue has been discovered while digging into
    9d33a5a804db.
    
    Author: Michael Paquier <michael@paquier.xyz>
    Discussion: https://postgr.es/m/aioT7ui_ZJ9RMlfM@paquier.xyz
    Backpatch-through: 14


 src/backend/utils/adt/xml.c         | 4 +++-
 src/test/regress/expected/xml.out   | 6 ++++++
 src/test/regress/expected/xml_1.out | 5 +++++
 src/test/regress/sql/xml.sql        | 1 +
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 2c7f778cfdb..0953ad2becb 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -4199,7 +4199,9 @@ xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt)
 {
 	xmltype    *result = NULL;
 
-	if (cur->type != XML_ATTRIBUTE_NODE && cur->type != XML_TEXT_NODE)
+	if (cur->type != XML_ATTRIBUTE_NODE &&
+		cur->type != XML_TEXT_NODE &&
+		cur->type != XML_NAMESPACE_DECL)
 	{
 		void		(*volatile nodefree) (xmlNodePtr) = NULL;
 		volatile xmlBufferPtr buf = NULL;
diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index 449733f8ae9..3e80a7ff465 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -944,6 +944,12 @@ SELECT xpath('root', '<root/>');
  {<root/>}
 (1 row)
 
+SELECT xpath('//namespace::foo', '<root xmlns:foo="http://127.0.0.1"/>');
+       xpath        
+--------------------
+ {http://127.0.0.1}
+(1 row)
+
 -- Round-trip non-ASCII data through xpath().
 DO $$
 DECLARE
diff --git a/src/test/regress/expected/xml_1.out b/src/test/regress/expected/xml_1.out
index a962fce36b9..2697c68a511 100644
--- a/src/test/regress/expected/xml_1.out
+++ b/src/test/regress/expected/xml_1.out
@@ -687,6 +687,11 @@ ERROR:  unsupported XML feature
 LINE 1: SELECT xpath('root', '<root/>');
                              ^
 DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xpath('//namespace::foo', '<root xmlns:foo="http://127.0.0.1"/>');
+ERROR:  unsupported XML feature
+LINE 1: SELECT xpath('//namespace::foo', '<root xmlns:foo="http://12...
+                                         ^
+DETAIL:  This functionality requires the server to be built with libxml support.
 -- Round-trip non-ASCII data through xpath().
 DO $$
 DECLARE
diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index a771a441c36..2b8445e499e 100644
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -244,6 +244,7 @@ SELECT xpath('count(//*)=3', '<root><sub/><sub/></root>');
 SELECT xpath('name(/*)', '<root><sub/><sub/></root>');
 SELECT xpath('/nosuchtag', '<root/>');
 SELECT xpath('root', '<root/>');
+SELECT xpath('//namespace::foo', '<root xmlns:foo="http://127.0.0.1"/>');
 
 -- Round-trip non-ASCII data through xpath().
 DO $$