Initial SQL/XML support: xml data type and initial set of functions.

src/backend/utils/adt/xml.c

@@ -0,0 +1,942 @@
+/*-------------------------------------------------------------------------
+ *
+ * xml.c
+ *	  XML data type support.
+ *
+ *
+ * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.1 2006/12/21 16:05:15 petere Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * Generally, XML type support is only available when libxml use was
+ * configured during the build.  But even if that is not done, the
+ * type and all the functions are available, but most of them will
+ * fail.  For one thing, this avoids having to manage variant catalog
+ * installations.  But it also has nice effects such as that you can
+ * dump a database containing XML type data even if the server is not
+ * linked with libxml.
+ */
+
+#include "postgres.h"
+
+#ifdef USE_LIBXML
+#include <libxml/chvalid.h>
+#include <libxml/parser.h>
+#include <libxml/tree.h>
+#include <libxml/uri.h>
+#include <libxml/xmlerror.h>
+#endif /* USE_LIBXML */
+
+#include "fmgr.h"
+#include "mb/pg_wchar.h"
+#include "nodes/execnodes.h"
+#include "utils/builtins.h"
+#include "utils/xml.h"
+
+
+#ifdef USE_LIBXML
+
+/*
+ * A couple of useful macros (similar to ones from libxml/parse.c)
+ */
+#define CMP4( s, c1, c2, c3, c4 ) \
+  ( ((unsigned char *) s)[ 0 ] == c1 && ((unsigned char *) s)[ 1 ] == c2 && \
+    ((unsigned char *) s)[ 2 ] == c3 && ((unsigned char *) s)[ 3 ] == c4 )
+#define CMP5( s, c1, c2, c3, c4, c5 ) \
+  ( CMP4( s, c1, c2, c3, c4 ) && ((unsigned char *) s)[ 4 ] == c5 )
+
+#define PG_XML_DEFAULT_URI "dummy.xml"
+#define XML_ERRBUF_SIZE 200
+
+
+static void 	xml_init(void);
+static void    *xml_palloc(size_t size);
+static void    *xml_repalloc(void *ptr, size_t size);
+static void 	xml_pfree(void *ptr);
+static char    *xml_pstrdup(const char *string);
+static void 	xml_ereport(int level, char *msg, void *ctxt);
+static void 	xml_errorHandler(void *ctxt, const char *msg, ...);
+static void 	xml_ereport_by_code(int level, char *msg, int errcode);
+static xmlChar *xml_text2xmlChar(text *in);
+static xmlDocPtr xml_parse(text *data, int opts, bool is_document);
+
+
+/* Global variables */
+/* taken from contrib/xml2 */
+/* FIXME: DO NOT USE global vars !!! */
+char	   *xml_errbuf;				/* per line error buffer */
+char	   *xml_errmsg = NULL;		/* overall error message */
+
+#endif /* USE_LIBXML */
+
+
+#define NO_XML_SUPPORT() ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("no XML support in this installation")))
+
+
+Datum
+xml_in(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	char		*s = PG_GETARG_CSTRING(0);
+	size_t		len;
+	xmltype		*vardata;
+
+	len = strlen(s);
+	vardata = palloc(len + VARHDRSZ);
+	VARATT_SIZEP(vardata) = len + VARHDRSZ;
+	memcpy(VARDATA(vardata), s, len);
+
+	/*
+	 * Parse the data to check if it is well-formed XML data.  Assume
+	 * that ERROR occurred if parsing failed.  Do we need DTD
+	 * validation (if DTD exists)?
+	 */
+	xml_parse(vardata, XML_PARSE_DTDATTR | XML_PARSE_DTDVALID, false);
+
+	PG_RETURN_XML_P(vardata);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+Datum
+xml_out(PG_FUNCTION_ARGS)
+{
+	xmltype		*s = PG_GETARG_XML_P(0);
+	char		*result;
+	int32		len;
+	
+	len = VARSIZE(s) - VARHDRSZ;
+	result = palloc(len + 1);
+	memcpy(result, VARDATA(s), len);
+	result[len] = '\0';
+	
+	PG_RETURN_CSTRING(result);
+}
+
+
+#ifdef USE_LIBXML
+static void
+appendStringInfoText(StringInfo str, const text *t)
+{
+	appendBinaryStringInfo(str, VARDATA(t), VARSIZE(t) - VARHDRSZ);
+}
+
+
+static xmltype *
+stringinfo_to_xmltype(StringInfo buf)
+{
+	int32 len;
+	xmltype *result;
+
+	len = buf->len + VARHDRSZ;
+	result = palloc(len);
+	VARATT_SIZEP(result) = len;
+	memcpy(VARDATA(result), buf->data, buf->len);
+
+	return result;
+}
+#endif
+
+
+Datum
+xmlcomment(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text *arg = PG_GETARG_TEXT_P(0);
+	int len =  VARATT_SIZEP(arg) - VARHDRSZ;
+	StringInfoData buf;
+	int i;
+
+	/* check for "--" in string or "-" at the end */
+	for (i = 1; i < len; i++)
+		if ((VARDATA(arg)[i] == '-' && VARDATA(arg)[i - 1] == '-')
+			|| (VARDATA(arg)[i] == '-' && i == len - 1))
+					ereport(ERROR,
+							(errcode(ERRCODE_INVALID_XML_COMMENT),
+							 errmsg("invalid XML comment")));
+
+	initStringInfo(&buf);
+	appendStringInfo(&buf, "<!--");
+	appendStringInfoText(&buf, arg);
+	appendStringInfo(&buf, "-->");
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(&buf));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+Datum
+xmlparse(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *data;
+	bool		is_document;
+	bool		preserve_whitespace;
+
+	data = PG_GETARG_TEXT_P(0);
+
+	if (PG_NARGS() >= 2)
+		is_document = PG_GETARG_BOOL(1);
+	else
+		is_document = false;
+
+	if (PG_NARGS() >= 3)
+		preserve_whitespace = PG_GETARG_BOOL(2);
+	else
+		/*
+		 * Since the XMLPARSE grammar makes STRIP WHITESPACE the
+		 * default, this argument should really default to false.  But
+		 * until we have actually implemented whitespace stripping,
+		 * this would be annoying.
+		 */
+		preserve_whitespace = true;
+
+	if (!preserve_whitespace)
+		ereport(WARNING,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("XMLPARSE with STRIP WHITESPACE is not implemented")));
+
+	/*
+	 * Note, that here we try to apply DTD defaults
+	 * (XML_PARSE_DTDATTR) according to SQL/XML:10.16.7.d: 'Default
+	 * valies defined by internal DTD are applied'.  As for external
+	 * DTDs, we try to support them too, (see SQL/XML:10.16.7.e)
+	 */
+	xml_parse(data, XML_PARSE_DTDATTR, is_document); /* assume that ERROR occurred if parsing failed */
+
+	PG_RETURN_XML_P(data);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+Datum
+xmlpi(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	char	   *target = NameStr(*PG_GETARG_NAME(0));
+	StringInfoData buf;
+
+	if (strlen(target) >= 3
+		&& (target[0] == 'x' || target[0] == 'X')
+		&& (target[1] == 'm' || target[1] == 'M')
+		&& (target[2] == 'l' || target[2] == 'L'))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("invalid XML processing instruction"),
+				 errdetail("XML processing instruction target name cannot start with \"xml\".")));
+	}
+
+	initStringInfo(&buf);
+
+	appendStringInfo(&buf, "<?");
+	appendStringInfoString(&buf, map_sql_identifier_to_xml_name(target, false));
+	if (PG_NARGS() > 1)
+	{
+		text *arg = PG_GETARG_TEXT_P(1);
+		char *string;
+
+		string = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(arg)));
+		if (strstr(string, "?>"))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_XML_PROCESSING_INSTRUCTION),
+				 errmsg("invalid XML processing instruction"),
+				 errdetail("XML processing instruction cannot contain \"?>\".")));
+
+		appendStringInfoString(&buf, " ");
+		appendStringInfoString(&buf, string);
+	}
+	appendStringInfoString(&buf, "?>");
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(&buf));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+Datum
+xmlroot(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	xmltype	   *data;
+	text	   *version;
+	int			standalone;
+	StringInfoData buf;
+
+	if (PG_ARGISNULL(0))
+		PG_RETURN_NULL();
+	else
+		data = PG_GETARG_XML_P(0);
+
+	if (PG_ARGISNULL(1))
+		version = NULL;
+	else
+		version = PG_GETARG_TEXT_P(1);
+
+	if (PG_ARGISNULL(2))
+		standalone = 0;
+	else
+	{
+		bool tmp = PG_GETARG_BOOL(2);
+		standalone = (tmp ? 1 : -1);
+	}
+
+	/*
+	 * FIXME: This is probably supposed to be cleverer if there
+	 * already is an XML preamble.
+	 */
+	initStringInfo(&buf);
+
+	appendStringInfo(&buf,"<?xml");
+	if (version) {
+		appendStringInfo(&buf, " version=\"");
+		appendStringInfoText(&buf, version);
+		appendStringInfo(&buf, "\"");
+	}
+	if (standalone)
+		appendStringInfo(&buf, " standalone=\"%s\"", (standalone == 1 ? "yes" : "no"));
+	appendStringInfo(&buf, "?>");
+	appendStringInfoText(&buf, (text *) data);
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(&buf));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+/*
+ * Validate document (given as string) against DTD (given as external link)
+ * TODO !!! use text instead of cstring for second arg
+ * TODO allow passing DTD as a string value (not only as an URI)
+ * TODO redesign (see comment with '!!!' below)
+ */
+Datum
+xmlvalidate(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text				*data = PG_GETARG_TEXT_P(0);
+	text				*dtdOrUri = PG_GETARG_TEXT_P(1);
+	bool				result = FALSE;
+	xmlParserCtxtPtr	ctxt; /* the parser context */
+	xmlDocPtr 			doc; /* the resulting document tree */
+	xmlDtdPtr			dtd;
+
+	xml_init();
+
+	ctxt = xmlNewParserCtxt();
+	if (ctxt == NULL)
+		xml_ereport(ERROR, "could not allocate parser context", ctxt);
+	doc = xmlCtxtReadMemory(ctxt, (char *) VARDATA(data), 
+							VARSIZE(data) - VARHDRSZ, PG_XML_DEFAULT_URI, NULL, 0);
+	if (doc == NULL)
+		xml_ereport(ERROR, "could not parse XML data", ctxt);
+
+#if 0
+	uri = xmlCreateURI();
+	ereport(NOTICE, (errcode(0),errmsg(" dtd - %s", dtdOrUri)));
+	dtd = palloc(sizeof(xmlDtdPtr));
+	uri = xmlParseURI(dtdOrUri);
+	if (uri == NULL)
+		xml_ereport(ERROR, "not implemented yet... (TODO)", ctxt);
+	else
+#endif
+		dtd = xmlParseDTD(NULL, xml_text2xmlChar(dtdOrUri));
+
+	if (dtd == NULL)
+	{
+#if 0
+		xmlFreeDoc(doc);
+		xmlFreeParserCtxt(ctxt);
+#endif
+		xml_ereport(ERROR, "could not load DTD", ctxt);
+	}
+
+	if (xmlValidateDtd(xmlNewValidCtxt(), doc, dtd) == 1)
+		result = TRUE;
+	
+#if 0
+	xmlFreeURI(uri);
+	xmlFreeDtd(dtd);
+	xmlFreeDoc(doc);
+	xmlFreeParserCtxt(ctxt);
+	xmlCleanupParser();
+#endif
+	
+	if (!result)
+		xml_ereport(NOTICE, "validation against DTD failed", ctxt);
+
+	PG_RETURN_BOOL(result);
+#else /* not USE_LIBXML */
+	NO_XML_SUPPORT();
+	return 0;
+#endif /* not USE_LIBXML */
+}
+
+
+#ifdef USE_LIBXML
+
+/*
+ * Container for some init stuff (not good design!)
+ * TODO xmlChar is utf8-char, make proper tuning (initdb with enc!=utf8 and check)
+ */
+static void
+xml_init(void)
+{
+	/*
+	 * Currently, we have no pure UTF-8 support for internals -- check
+	 * if we can work.
+	 */
+	if (sizeof (char) != sizeof (xmlChar))
+		ereport(ERROR, 
+				(errmsg("cannot initialize XML library"),
+				 errdetail("libxml2 has incompatible char type: sizeof(char)=%u, sizeof(xmlChar)=%u.", 
+						   sizeof(char), sizeof(xmlChar))));
+	
+	xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
+	xmlInitParser();
+	LIBXML_TEST_VERSION;
+	/* do not flood PG's logfile with libxml error messages - reset error handler*/ 
+	xmlSetGenericErrorFunc(NULL, xml_errorHandler);
+	xml_errmsg = NULL;
+	xml_errbuf = palloc(XML_ERRBUF_SIZE);
+	memset(xml_errbuf, 0, XML_ERRBUF_SIZE);
+}
+
+
+/*
+ * Convert a C string to XML internal representation
+ * (same things as for TEXT, but with checking the data for well-formedness
+ * and, moreover, validation against DTD, if needed).
+ * NOTICE: We use TEXT type as internal storage type. In the future,
+ * we plan to create own storage type (maybe several types/strategies)
+ * TODO predefined DTDs / XSDs and validation
+ * TODO validation against XML Schema
+ * TODO maybe, libxml2's xmlreader is better? (do not construct DOM, yet do not use SAX - see xml_reader.c)
+ * TODO what about internal URI for docs? (see PG_XML_DEFAULT_URI below)
+ */
+static xmlDocPtr
+xml_parse(text *data, int opts, bool is_document)
+{
+	bool				validationFailed = FALSE;
+	xmlParserCtxtPtr 	ctxt; /* the parser context */
+	xmlDocPtr 			doc; /* the resulting document tree */
+	int					res_code;
+	int32				len;
+	xmlChar				*string;
+#ifdef XML_DEBUG_DTD_CONST
+	xmlDtdPtr			dtd; /* pointer to DTD */
+#endif
+
+	xml_init();
+	
+	len = VARSIZE(data) - VARHDRSZ; /* will be useful later */
+	string = xml_text2xmlChar(data);
+	
+	ctxt = xmlNewParserCtxt();
+	if (ctxt == NULL)
+		xml_ereport(ERROR, "could not allocate parser context", ctxt);
+	
+	/* first, we try to parse the string as it is XML doc, then, as XML chunk */
+	ereport(DEBUG3, (errmsg("string to parse: %s", string)));
+	if (len > 4 && CMP5(string, '<', '?', 'x', 'm', 'l'))
+	{
+		/* consider it as DOCUMENT */
+		doc = xmlCtxtReadMemory(ctxt, string, len, PG_XML_DEFAULT_URI, NULL, opts);
+		if (doc == NULL)
+		{
+			xml_ereport(ERROR, "could not parse XML data", ctxt);
+#if 0
+			xmlFreeParserCtxt(ctxt);
+			xmlCleanupParser();
+			ereport(ERROR, (errmsg("could not parse XML data")));
+#endif
+		}
+	}
+	else
+	{
+		/* attempt to parse the string as if it is an XML fragment */
+		ereport(DEBUG3, (errmsg("the string is not an XML doc, trying to parse as a CHUNK")));
+		doc = xmlNewDoc(NULL);
+		/* TODO resolve: xmlParseBalancedChunkMemory assumes that string is UTF8 encoded! */
+		res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0, string, NULL);
+		if (res_code != 0)
+		{
+			xmlFreeParserCtxt(ctxt);
+			xmlCleanupParser();
+			xml_ereport_by_code(ERROR, "could not parse XML data", res_code);
+		}
+	}
+
+#ifdef XML_DEBUG_DTD_CONST
+	dtd = xmlParseDTD(NULL, (xmlChar *) XML_DEBUG_DTD_CONST);
+	xml_ereport(DEBUG3, "solid path to DTD was defined for debugging purposes", ctxt);
+	if (dtd == NULL)
+	{
+		xml_ereport(ERROR, "could not parse DTD data", ctxt);
+	}
+	else
+#else
+	/* if dtd for our xml data is detected... */
+	if ((doc->intSubset != NULL) || (doc->extSubset != NULL))
+#endif
+	{
+		/* assume that inline DTD exists - validation should be performed */
+#ifdef XML_DEBUG_DTD_CONST
+		if (xmlValidateDtd(xmlNewValidCtxt(), doc, dtd) != 1)
+#else
+		if (ctxt->valid == 0)
+#endif
+		{
+			/* DTD exists, but validator reported 'validation failed' */
+			validationFailed = TRUE;
+		}
+	}
+	
+	if (validationFailed)
+		xml_ereport(WARNING, "validation against DTD failed", ctxt);
+	
+	/* TODO encoding issues 
+	 * (thoughts:
+	 * 		CASE:
+	 *   		- XML data has explicit encoding attribute in its prolog
+	 *   		- if not, assume that enc. of XML data is the same as client's one
+	 * 
+	 * 		The common rule is to accept the XML data only if its encoding
+	 * 		is the same as encoding of the storage (server's). The other possible
+	 * 		option is to accept all the docs, but DO TRANSFORMATION and, if needed,
+	 * 		change the prolog.
+	 * 
+	 * 		I think I'd stick the first way (for the 1st version), 
+	 * 		it's much simplier (less errors...)
+	 * ) */
+	/* ... */
+	
+	xmlFreeParserCtxt(ctxt);
+	xmlCleanupParser();
+	
+	ereport(DEBUG3, (errmsg("XML data successfully parsed, encoding: %s", 
+		(char *) doc->encoding)));
+	
+	return doc;
+}
+
+
+/* 
+ * xmlChar<->text convertions 
+ */
+static xmlChar *
+xml_text2xmlChar(text *in)
+{
+	int32 		len = VARSIZE(in) - VARHDRSZ;
+	xmlChar		*res;
+
+	res = palloc(len + 1);
+	memcpy(res, VARDATA(in), len);
+	res[len] = '\0';
+	
+	return(res);
+}
+
+
+/* 
+ * Wrappers for memory management functions 
+ */
+static void *
+xml_palloc(size_t size)
+{
+	return palloc(size);
+}
+
+
+static void *
+xml_repalloc(void *ptr, size_t size)
+{
+	return repalloc(ptr, size);
+}
+
+
+static void
+xml_pfree(void *ptr)
+{
+	pfree(ptr);
+}
+
+
+static char *
+xml_pstrdup(const char *string)
+{
+	return pstrdup(string);
+}
+
+
+/*
+ * Wrapper for "ereport" function. 
+ * Adds detail - libxml's native error message, if any.
+ */
+static void
+xml_ereport(int level, char *msg, void *ctxt)
+{
+	char *xmlErrDetail;
+	int xmlErrLen, i;
+	xmlErrorPtr libxmlErr = NULL;
+	
+	if (xml_errmsg != NULL)
+	{
+		ereport(DEBUG1, (errmsg("%s", xml_errmsg)));
+		pfree(xml_errmsg);
+	}
+	
+	if (ctxt != NULL)
+		libxmlErr = xmlCtxtGetLastError(ctxt);
+	
+	if (libxmlErr == NULL)
+	{
+		if (level == ERROR)
+		{
+			xmlFreeParserCtxt(ctxt);
+			xmlCleanupParser();
+		}
+		ereport(level, (errmsg(msg)));
+	}
+	else
+	{
+		/* as usual, libxml error message contains '\n'; get rid of it */
+		xmlErrLen = strlen(libxmlErr->message); /* - 1; */
+		xmlErrDetail = (char *) palloc(xmlErrLen);
+		for (i = 0; i < xmlErrLen; i++)
+		{
+			if (libxmlErr->message[i] == '\n')
+				xmlErrDetail[i] = '.';
+			else
+				xmlErrDetail[i] = libxmlErr->message[i];
+		}
+		if (level == ERROR)
+		{
+			xmlFreeParserCtxt(ctxt);
+			xmlCleanupParser();
+		}
+		ereport(level, (errmsg(msg), errdetail("%s", xmlErrDetail)));
+	}
+}
+
+
+/*
+ * Error handler for libxml error messages
+ */
+static void
+xml_errorHandler(void *ctxt, const char *msg,...)
+{
+	va_list		args;
+	
+	va_start(args, msg);
+	vsnprintf(xml_errbuf, XML_ERRBUF_SIZE, msg, args);
+	va_end(args);
+	/* Now copy the argument across */
+	if (xml_errmsg == NULL)
+		xml_errmsg = pstrdup(xml_errbuf);
+	else
+	{
+		int32		xsize = strlen(xml_errmsg);
+
+		xml_errmsg = repalloc(xml_errmsg, (size_t) (xsize + strlen(xml_errbuf) + 1));
+		strncpy(&xml_errmsg[xsize - 1], xml_errbuf, strlen(xml_errbuf));
+		xml_errmsg[xsize + strlen(xml_errbuf) - 1] = '\0';
+	}
+	memset(xml_errbuf, 0, XML_ERRBUF_SIZE);
+}
+
+
+/*
+ * Return error message by libxml error code
+ * TODO make them closer to recommendations from Postgres manual
+ */
+static void
+xml_ereport_by_code(int level, char *msg, int code)
+{
+    const char *det;
+
+	if (code < 0)
+	{
+		ereport(level, (errmsg(msg)));
+		return;
+	}
+
+    switch (code) {
+        case XML_ERR_INTERNAL_ERROR:
+            det = "libxml internal error";
+            break;
+        case XML_ERR_ENTITY_LOOP:
+            det = "Detected an entity reference loop";
+            break;
+        case XML_ERR_ENTITY_NOT_STARTED:
+            det = "EntityValue: \" or ' expected";
+            break;
+        case XML_ERR_ENTITY_NOT_FINISHED:
+            det = "EntityValue: \" or ' expected";
+            break;
+        case XML_ERR_ATTRIBUTE_NOT_STARTED:
+            det = "AttValue: \" or ' expected";
+            break;
+        case XML_ERR_LT_IN_ATTRIBUTE:
+            det = "Unescaped '<' not allowed in attributes values";
+            break;
+        case XML_ERR_LITERAL_NOT_STARTED:
+            det = "SystemLiteral \" or ' expected";
+            break;
+        case XML_ERR_LITERAL_NOT_FINISHED:
+            det = "Unfinished System or Public ID \" or ' expected";
+            break;
+        case XML_ERR_MISPLACED_CDATA_END:
+            det = "Sequence ']]>' not allowed in content";
+            break;
+        case XML_ERR_URI_REQUIRED:
+            det = "SYSTEM or PUBLIC, the URI is missing";
+            break;
+        case XML_ERR_PUBID_REQUIRED:
+            det = "PUBLIC, the Public Identifier is missing";
+            break;
+        case XML_ERR_HYPHEN_IN_COMMENT:
+            det = "Comment must not contain '--' (double-hyphen)";
+            break;
+        case XML_ERR_PI_NOT_STARTED:
+            det = "xmlParsePI : no target name";
+            break;
+        case XML_ERR_RESERVED_XML_NAME:
+            det = "Invalid PI name";
+            break;
+        case XML_ERR_NOTATION_NOT_STARTED:
+            det = "NOTATION: Name expected here";
+            break;
+        case XML_ERR_NOTATION_NOT_FINISHED:
+            det = "'>' required to close NOTATION declaration";
+            break;
+        case XML_ERR_VALUE_REQUIRED:
+            det = "Entity value required";
+            break;
+        case XML_ERR_URI_FRAGMENT:
+            det = "Fragment not allowed";
+            break;
+        case XML_ERR_ATTLIST_NOT_STARTED:
+            det = "'(' required to start ATTLIST enumeration";
+            break;
+        case XML_ERR_NMTOKEN_REQUIRED:
+            det = "NmToken expected in ATTLIST enumeration";
+            break;
+        case XML_ERR_ATTLIST_NOT_FINISHED:
+            det = "')' required to finish ATTLIST enumeration";
+            break;
+        case XML_ERR_MIXED_NOT_STARTED:
+            det = "MixedContentDecl : '|' or ')*' expected";
+            break;
+        case XML_ERR_PCDATA_REQUIRED:
+            det = "MixedContentDecl : '#PCDATA' expected";
+            break;
+        case XML_ERR_ELEMCONTENT_NOT_STARTED:
+            det = "ContentDecl : Name or '(' expected";
+            break;
+        case XML_ERR_ELEMCONTENT_NOT_FINISHED:
+            det = "ContentDecl : ',' '|' or ')' expected";
+            break;
+        case XML_ERR_PEREF_IN_INT_SUBSET:
+            det = "PEReference: forbidden within markup decl in internal subset";
+            break;
+        case XML_ERR_GT_REQUIRED:
+            det = "Expected '>'";
+            break;
+        case XML_ERR_CONDSEC_INVALID:
+            det = "XML conditional section '[' expected";
+            break;
+        case XML_ERR_EXT_SUBSET_NOT_FINISHED:
+            det = "Content error in the external subset";
+            break;
+        case XML_ERR_CONDSEC_INVALID_KEYWORD:
+            det = "conditional section INCLUDE or IGNORE keyword expected";
+            break;
+        case XML_ERR_CONDSEC_NOT_FINISHED:
+            det = "XML conditional section not closed";
+            break;
+        case XML_ERR_XMLDECL_NOT_STARTED:
+            det = "Text declaration '<?xml' required";
+            break;
+        case XML_ERR_XMLDECL_NOT_FINISHED:
+            det = "parsing XML declaration: '?>' expected";
+            break;
+        case XML_ERR_EXT_ENTITY_STANDALONE:
+            det = "external parsed entities cannot be standalone";
+            break;
+        case XML_ERR_ENTITYREF_SEMICOL_MISSING:
+            det = "EntityRef: expecting ';'";
+            break;
+        case XML_ERR_DOCTYPE_NOT_FINISHED:
+            det = "DOCTYPE improperly terminated";
+            break;
+        case XML_ERR_LTSLASH_REQUIRED:
+            det = "EndTag: '</' not found";
+            break;
+        case XML_ERR_EQUAL_REQUIRED:
+            det = "Expected '='";
+            break;
+        case XML_ERR_STRING_NOT_CLOSED:
+            det = "String not closed expecting \" or '";
+            break;
+        case XML_ERR_STRING_NOT_STARTED:
+            det = "String not started expecting ' or \"";
+            break;
+        case XML_ERR_ENCODING_NAME:
+            det = "Invalid XML encoding name";
+            break;
+        case XML_ERR_STANDALONE_VALUE:
+            det = "Standalone accepts only 'yes' or 'no'";
+            break;
+        case XML_ERR_DOCUMENT_EMPTY:
+            det = "Document is empty";
+            break;
+        case XML_ERR_DOCUMENT_END:
+            det = "Extra content at the end of the document";
+            break;
+        case XML_ERR_NOT_WELL_BALANCED:
+            det = "Chunk is not well balanced";
+            break;
+        case XML_ERR_EXTRA_CONTENT:
+            det = "Extra content at the end of well balanced chunk";
+            break;
+        case XML_ERR_VERSION_MISSING:
+            det = "Malformed declaration expecting version";
+            break;
+        /* more err codes... Please, keep the order! */
+        case XML_ERR_ATTRIBUTE_WITHOUT_VALUE: /* 41 */
+        	det ="Attribute without value";
+        	break;
+        case XML_ERR_ATTRIBUTE_REDEFINED:
+        	det ="Attribute defined more than once in the same element";
+        	break;
+        case XML_ERR_COMMENT_NOT_FINISHED: /* 45 */
+            det = "Comment is not finished";
+            break;
+        case XML_ERR_NAME_REQUIRED: /* 68 */
+            det = "Element name not found";
+            break;
+        case XML_ERR_TAG_NOT_FINISHED: /* 77 */
+            det = "Closing tag not found";
+            break;
+        default:
+            det = "Unregistered error (libxml error code: %d)";
+            ereport(DEBUG1, (errmsg("Check out \"libxml/xmlerror.h\" and bring errcode \"%d\" processing to \"xml.c\".", code)));
+    }
+    
+	if (xml_errmsg != NULL)
+	{
+		ereport(DEBUG1, (errmsg("%s", xml_errmsg)));
+		pfree(xml_errmsg);
+	}
+    
+	ereport(level, (errmsg(msg), errdetail(det, code)));
+}
+
+
+/*
+ * Convert one char in the current server encoding to a Unicode
+ * codepoint.
+ */
+static pg_wchar
+sqlchar_to_unicode(unsigned char *s)
+{
+	int save_enc;
+	pg_wchar ret;
+	char *utf8string = pg_do_encoding_conversion(s, pg_mblen(s), GetDatabaseEncoding(), PG_UTF8);
+
+	save_enc = GetDatabaseEncoding();
+	SetDatabaseEncoding(PG_UTF8);
+	pg_mb2wchar_with_len(utf8string, &ret, pg_mblen(s));
+	SetDatabaseEncoding(save_enc);
+
+	return ret;
+}
+
+
+static bool
+is_valid_xml_namefirst(pg_wchar c)
+{
+	/* (Letter | '_' | ':') */
+	return (xmlIsBaseCharQ(c) || xmlIsIdeographicQ(c)
+			|| c == '_' || c == ':');
+}
+
+
+static bool
+is_valid_xml_namechar(pg_wchar c)
+{
+	/* Letter | Digit | '.' | '-' | '_' | ':' | CombiningChar | Extender */
+	return (xmlIsBaseCharQ(c) || xmlIsIdeographicQ(c)
+			|| xmlIsDigitQ(c)
+			|| c == '.' || c == '-' || c == '_' || c == ':'
+			|| xmlIsCombiningQ(c)
+			|| xmlIsExtenderQ(c));
+}
+#endif /* USE_LIBXML */
+
+
+/*
+ * Map SQL identifier to XML name; see SQL/XML:2003 section 9.1.
+ */
+char *
+map_sql_identifier_to_xml_name(unsigned char *ident, bool fully_escaped)
+{
+#ifdef USE_LIBXML
+	StringInfoData buf;
+	unsigned char *p;
+
+	initStringInfo(&buf);
+
+	for (p = ident; *p; p += pg_mblen(p))
+	{
+		if (*p == ':' && (p == ident || fully_escaped))
+			appendStringInfo(&buf, "_x003A_");
+		else if (*p == '_' && *(p+1) == 'x')
+			appendStringInfo(&buf, "_x005F_");
+		else if (fully_escaped && p == ident
+				 && ( *p == 'x' || *p == 'X')
+				 && ( *(p+1) == 'm' || *(p+1) == 'M')
+				 && ( *(p+2) == 'l' || *(p+2) == 'L'))
+		{
+			if (*p == 'x')
+				appendStringInfo(&buf, "_x0078_");
+			else
+				appendStringInfo(&buf, "_x0058_");
+		}
+		else
+		{
+			pg_wchar u = sqlchar_to_unicode(p);
+
+			if (!is_valid_xml_namechar(u)
+				|| (p == ident && !is_valid_xml_namefirst(u)))
+			appendStringInfo(&buf, "_x%04X_", (unsigned int) u);
+			else
+				appendBinaryStringInfo(&buf, p, pg_mblen(p));
+		}
+	}
+
+	return buf.data;
+#else /* not USE_LIBXML */
+	NO_XML_SUPPORT();
+	return NULL;
+#endif /* not USE_LIBXML */
+}