Fix namespace handling in xpath function

Previously, the xml value resulting from an xpath query would not have
namespace declarations if the namespace declarations were attached to
an ancestor element in the input xml value.  That means the output value
was not correct XML.  Fix that by running the result value through
xmlCopyNode(), which produces the correct namespace declarations.

Author: Ali Akbar <the.apaan@gmail.com>

1 files changed, 26 insertions, 8 deletions

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index a735aa28015..bfe9447295d 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -141,9 +141,10 @@ static bool print_xml_decl(StringInfo buf, const xmlChar *version,
 			   pg_enc encoding, int standalone);
 static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
 		  bool preserve_whitespace, int encoding);
-static text *xml_xmlnodetoxmltype(xmlNodePtr cur);
+static text *xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt);
 static int xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
-					   ArrayBuildState *astate);
+					   ArrayBuildState *astate,
+					   PgXmlErrorContext *xmlerrcxt);
 #endif   /* USE_LIBXML */
 
 static StringInfo query_to_xml_internal(const char *query, char *tablename,
@@ -3599,26 +3600,41 @@ SPI_sql_row_to_xmlelement(int rownum, StringInfo result, char *tablename,
  * return value otherwise)
  */
 static text *
-xml_xmlnodetoxmltype(xmlNodePtr cur)
+xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt)
 {
 	xmltype    *result;
 
 	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);
+
+		if (cur_copy == NULL)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not copy node");
+
 		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
@@ -3660,7 +3676,8 @@ xml_xmlnodetoxmltype(xmlNodePtr cur)
  */
 static int
 xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
-					   ArrayBuildState *astate)
+					   ArrayBuildState *astate,
+					   PgXmlErrorContext *xmlerrcxt)
 {
 	int			result = 0;
 	Datum		datum;
@@ -3679,7 +3696,8 @@ xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 
 					for (i = 0; i < result; i++)
 					{
-						datum = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i]));
+						datum = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i],
+																	 xmlerrcxt));
 						(void) accumArrayResult(astate, datum, false,
 												XMLOID, CurrentMemoryContext);
 					}
@@ -3881,9 +3899,9 @@ xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
 		 * Extract the results as requested.
 		 */
 		if (res_nitems != NULL)
-			*res_nitems = xml_xpathobjtoxmlarray(xpathobj, astate);
+			*res_nitems = xml_xpathobjtoxmlarray(xpathobj, astate, xmlerrcxt);
 		else
-			(void) xml_xpathobjtoxmlarray(xpathobj, astate);
+			(void) xml_xpathobjtoxmlarray(xpathobj, astate, xmlerrcxt);
 	}
 	PG_CATCH();
 	{