At 2014-05-30 16:04:33 +0700, the.ap...@gmail.com wrote:
>
> While developing some XML processing queries, i stumbled on an old bug
> mentioned in http://wiki.postgresql.org/wiki/Todo#XML: Fix Nested or
> repeated xpath() that apparently mess up namespaces.

Thanks for the patch, and welcome to Postgres development.

I can confirm that it works fine. I have attached here a very slightly
tweaked version of the patch (removed trailing whitespace, and changed
some comment text).

I'm marking this ready for committer.

-- Abhijit
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 422be69..f9ad598 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -3602,19 +3602,28 @@ xml_xmlnodetoxmltype(xmlNodePtr cur)
 	if (cur->type == XML_ELEMENT_NODE)
 	{
 		xmlBufferPtr buf;
+		xmlNodePtr cur_copy;
 
 		buf = xmlBufferCreate();
+
+		/* the result of xmlNodeDump won't contain namespace definitions
+		 * from parent nodes, but xmlCopyNode duplicates a node along
+		 * with its required namespace definitions.
+		 */
+		cur_copy = xmlCopyNode(cur, 1);
 		PG_TRY();
 		{
-			xmlNodeDump(buf, NULL, cur, 0, 1);
+			xmlNodeDump(buf, NULL, cur_copy, 0, 1);
 			result = xmlBuffer_to_xmltype(buf);
 		}
 		PG_CATCH();
 		{
+			xmlFreeNode(cur_copy);
 			xmlBufferFree(buf);
 			PG_RE_THROW();
 		}
 		PG_END_TRY();
+		xmlFreeNode(cur_copy);
 		xmlBufferFree(buf);
 	}
 	else
diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index 382f9df..a6d26f7 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -584,6 +584,12 @@ SELECT xpath('//loc:piece/@id', '<local:data xmlns:local="http://127.0.0.1";><loc
  {1,2}
 (1 row)
 
+SELECT xpath('//loc:piece', '<local:data xmlns:local="http://127.0.0.1";><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc', 'http://127.0.0.1']]);
+                                                                     xpath                                                                      
+------------------------------------------------------------------------------------------------------------------------------------------------
+ {"<local:piece xmlns:local=\"http://127.0.0.1\"; id=\"1\">number one</local:piece>","<local:piece xmlns:local=\"http://127.0.0.1\"; id=\"2\"/>"}
+(1 row)
+
 SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
           xpath          
 -------------------------
diff --git a/src/test/regress/expected/xml_1.out b/src/test/regress/expected/xml_1.out
index a34d1f4..c7bcf91 100644
--- a/src/test/regress/expected/xml_1.out
+++ b/src/test/regress/expected/xml_1.out
@@ -498,6 +498,12 @@ LINE 1: SELECT xpath('//loc:piece/@id', '<local:data xmlns:local="ht...
                                         ^
 DETAIL:  This functionality requires the server to be built with libxml support.
 HINT:  You need to rebuild PostgreSQL using --with-libxml.
+SELECT xpath('//loc:piece', '<local:data xmlns:local="http://127.0.0.1";><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc', 'http://127.0.0.1']]);
+ERROR:  unsupported XML feature
+LINE 1: SELECT xpath('//loc:piece', '<local:data xmlns:local="http:/...
+                                    ^
+DETAIL:  This functionality requires the server to be built with libxml support.
+HINT:  You need to rebuild PostgreSQL using --with-libxml.
 SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
 ERROR:  unsupported XML feature
 LINE 1: SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>'...
diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index 90d4d67..241a5d6 100644
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -174,6 +174,7 @@ SELECT xpath(NULL, NULL) IS NULL FROM xmltest;
 SELECT xpath('', '<!-- error -->');
 SELECT xpath('//text()', '<local:data xmlns:local="http://127.0.0.1";><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>');
 SELECT xpath('//loc:piece/@id', '<local:data xmlns:local="http://127.0.0.1";><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc', 'http://127.0.0.1']]);
+SELECT xpath('//loc:piece', '<local:data xmlns:local="http://127.0.0.1";><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc', 'http://127.0.0.1']]);
 SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
 SELECT xpath('//text()', '<root>&lt;</root>');
 SELECT xpath('//@value', '<root value="&lt;"/>');
-- 
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