Use libxml's xmlwriter API for producing XML elements, instead of doing

our own printing dance.  This does a better job of quoting and escaping the
values.

Author: petere

src/backend/executor/execQual.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.204 2007/01/07 22:49:55 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.205 2007/01/10 20:33:54 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2654,7 +2654,6 @@ ExecEvalXml(XmlExprState *xmlExpr, ExprContext *econtext,
 	char		   *str;
 	ListCell 	   *arg;
 	ListCell   *narg;
-	bool	found_arg;
 	int 			i;
 
 	if (isDone)
@@ -2682,55 +2681,6 @@ ExecEvalXml(XmlExprState *xmlExpr, ExprContext *econtext,
 			}
 			break;
 
-		case IS_XMLELEMENT:
-			initStringInfo(&buf);
-			*isNull = false;
-			appendStringInfo(&buf, "<%s", xexpr->name);
-			i = 0;
-			forboth(arg, xmlExpr->named_args, narg, xexpr->arg_names)
-			{
-				ExprState 	*e = (ExprState *) lfirst(arg);
-				char	*argname = strVal(lfirst(narg));
-
-				value = ExecEvalExpr(e, econtext, &isnull, NULL);
-				if (!isnull)
-				{
-					str = OutputFunctionCall(&xmlExpr->named_outfuncs[i],
-											 value);
-					appendStringInfo(&buf, " %s=\"%s\"", argname, str);
-					pfree(str);
-				}
-				i++;
-			}
-
-			found_arg = false;
-			foreach(arg, xmlExpr->args)
-			{
-				ExprState 	*e = (ExprState *) lfirst(arg);
-
-				value = ExecEvalExpr(e, econtext, &isnull, NULL);
-				if (!isnull)
-				{
-					if (!found_arg)
-					{
-						appendStringInfoChar(&buf, '>');
-						found_arg = true;
-					}
-
-					/* we know the value is XML type */
-					str = DatumGetCString(DirectFunctionCall1(xml_out,
-															  value));
-					appendStringInfoString(&buf, str);
-					pfree(str);
-				}
-			}
-
-			if (!found_arg)
-				appendStringInfo(&buf, "/>");
-			else
-				appendStringInfo(&buf, "</%s>", xexpr->name);
-			break;
-
 		case IS_XMLFOREST:
 			initStringInfo(&buf);
 			i = 0;
@@ -2754,6 +2704,11 @@ ExecEvalXml(XmlExprState *xmlExpr, ExprContext *econtext,
 			break;
 
 			/* The remaining cases don't need to set up buf */
+		case IS_XMLELEMENT:
+			*isNull = false;
+			return PointerGetDatum(xmlelement(xmlExpr, econtext));
+			break;
+
 		case IS_XMLPARSE:
 			{
 				ExprState 	*e;

src/backend/utils/adt/xml.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.13 2007/01/07 22:49:56 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.14 2007/01/10 20:33:54 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,8 +32,10 @@
 #include <libxml/uri.h>
 #include <libxml/xmlerror.h>
 #include <libxml/xmlsave.h>
+#include <libxml/xmlwriter.h>
 #endif /* USE_LIBXML */
 
+#include "executor/executor.h"
 #include "fmgr.h"
 #include "libpq/pqformat.h"
 #include "mb/pg_wchar.h"
@@ -239,6 +241,71 @@ texttoxml(PG_FUNCTION_ARGS)
 }
 
 
+xmltype *
+xmlelement(XmlExprState *xmlExpr, ExprContext *econtext)
+{
+#ifdef USE_LIBXML
+	XmlExpr	   *xexpr = (XmlExpr *) xmlExpr->xprstate.expr;
+	int			i;
+	ListCell   *arg;
+	ListCell   *narg;
+	bool		isnull;
+	xmltype	   *result;
+	Datum		value;
+	char	   *str;
+
+	xmlBufferPtr buf;
+	xmlTextWriterPtr writer;
+
+	buf = xmlBufferCreate();
+	writer = xmlNewTextWriterMemory(buf, 0);
+
+	xmlTextWriterStartElement(writer, (xmlChar *) xexpr->name);
+
+	i = 0;
+	forboth(arg, xmlExpr->named_args, narg, xexpr->arg_names)
+	{
+		ExprState 	*e = (ExprState *) lfirst(arg);
+		char	*argname = strVal(lfirst(narg));
+
+		value = ExecEvalExpr(e, econtext, &isnull, NULL);
+		if (!isnull)
+		{
+			str = OutputFunctionCall(&xmlExpr->named_outfuncs[i], value);
+			xmlTextWriterWriteAttribute(writer, (xmlChar *) argname, (xmlChar *) str);
+			pfree(str);
+		}
+		i++;
+	}
+
+	foreach(arg, xmlExpr->args)
+	{
+		ExprState 	*e = (ExprState *) lfirst(arg);
+
+		value = ExecEvalExpr(e, econtext, &isnull, NULL);
+		if (!isnull)
+		{
+			/* we know the value is XML type */
+			str = DatumGetCString(DirectFunctionCall1(xml_out,
+													  value));
+			xmlTextWriterWriteRaw(writer, (xmlChar *) str);
+			pfree(str);
+		}
+	}
+
+	xmlTextWriterEndElement(writer);
+	xmlFreeTextWriter(writer);
+
+	result = xmlBuffer_to_xmltype(buf);
+	xmlBufferFree(buf);
+	return result;
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
 xmltype *
 xmlparse(text *data, bool is_document, bool preserve_whitespace)
 {
@@ -313,6 +380,7 @@ xmltype *
 xmlroot(xmltype *data, text *version, int standalone)
 {
 #ifdef USE_LIBXML
+	xmltype	   *result;
 	xmlDocPtr	doc;
 	xmlBufferPtr buffer;
 	xmlSaveCtxtPtr save;
@@ -344,7 +412,9 @@ xmlroot(xmltype *data, text *version, int standalone)
 
 	xmlFreeDoc(doc);
 
-	return xmlBuffer_to_xmltype(buffer);
+	result = xmlBuffer_to_xmltype(buffer);
+	xmlBufferFree(buffer);
+	return result;
 #else
 	NO_XML_SUPPORT();
 	return NULL;

src/include/utils/xml.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.7 2007/01/07 22:49:56 petere Exp $
+ * $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.8 2007/01/10 20:33:54 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,6 +16,7 @@
 #define XML_H
 
 #include "fmgr.h"
+#include "nodes/execnodes.h"
 
 typedef struct varlena xmltype;
 
@@ -32,6 +33,7 @@ extern Datum xmlcomment(PG_FUNCTION_ARGS);
 extern Datum texttoxml(PG_FUNCTION_ARGS);
 extern Datum xmlvalidate(PG_FUNCTION_ARGS);
 
+extern xmltype *xmlelement(XmlExprState *xmlExpr, ExprContext *econtext);
 extern xmltype *xmlparse(text *data, bool is_doc, bool preserve_whitespace);
 extern xmltype *xmlpi(char *target, text *arg, bool arg_is_null, bool *result_is_null);
 extern xmltype *xmlroot(xmltype *data, text *version, int standalone);