Adding upstream version 13.4.upstream/13.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4772 insertions, 0 deletions

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
new file mode 100644
index 0000000..4c29905
--- /dev/null
+++ b/src/backend/utils/adt/xml.c
@@ -0,0 +1,4772 @@
+/*-------------------------------------------------------------------------
+ *
+ * xml.c
+ *	  XML data type support.
+ *
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/utils/adt/xml.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * 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.  Thus, make sure xml_out() works even if nothing
+ * else does.
+ */
+
+/*
+ * Notes on memory management:
+ *
+ * Sometimes libxml allocates global structures in the hope that it can reuse
+ * them later on.  This makes it impractical to change the xmlMemSetup
+ * functions on-the-fly; that is likely to lead to trying to pfree() chunks
+ * allocated with malloc() or vice versa.  Since libxml might be used by
+ * loadable modules, eg libperl, our only safe choices are to change the
+ * functions at postmaster/backend launch or not at all.  Since we'd rather
+ * not activate libxml in sessions that might never use it, the latter choice
+ * is the preferred one.  However, for debugging purposes it can be awfully
+ * handy to constrain libxml's allocations to be done in a specific palloc
+ * context, where they're easy to track.  Therefore there is code here that
+ * can be enabled in debug builds to redirect libxml's allocations into a
+ * special context LibxmlContext.  It's not recommended to turn this on in
+ * a production build because of the possibility of bad interactions with
+ * external modules.
+ */
+/* #define USE_LIBXMLCONTEXT */
+
+#include "postgres.h"
+
+#ifdef USE_LIBXML
+#include <libxml/chvalid.h>
+#include <libxml/parser.h>
+#include <libxml/parserInternals.h>
+#include <libxml/tree.h>
+#include <libxml/uri.h>
+#include <libxml/xmlerror.h>
+#include <libxml/xmlversion.h>
+#include <libxml/xmlwriter.h>
+#include <libxml/xpath.h>
+#include <libxml/xpathInternals.h>
+
+/*
+ * We used to check for xmlStructuredErrorContext via a configure test; but
+ * that doesn't work on Windows, so instead use this grottier method of
+ * testing the library version number.
+ */
+#if LIBXML_VERSION >= 20704
+#define HAVE_XMLSTRUCTUREDERRORCONTEXT 1
+#endif
+#endif							/* USE_LIBXML */
+
+#include "access/htup_details.h"
+#include "access/table.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_class.h"
+#include "catalog/pg_type.h"
+#include "commands/dbcommands.h"
+#include "executor/spi.h"
+#include "executor/tablefunc.h"
+#include "fmgr.h"
+#include "lib/stringinfo.h"
+#include "libpq/pqformat.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "nodes/execnodes.h"
+#include "nodes/nodeFuncs.h"
+#include "utils/array.h"
+#include "utils/builtins.h"
+#include "utils/date.h"
+#include "utils/datetime.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/xml.h"
+
+
+/* GUC variables */
+int			xmlbinary;
+int			xmloption;
+
+#ifdef USE_LIBXML
+
+/* random number to identify PgXmlErrorContext */
+#define ERRCXT_MAGIC	68275028
+
+struct PgXmlErrorContext
+{
+	int			magic;
+	/* strictness argument passed to pg_xml_init */
+	PgXmlStrictness strictness;
+	/* current error status and accumulated message, if any */
+	bool		err_occurred;
+	StringInfoData err_buf;
+	/* previous libxml error handling state (saved by pg_xml_init) */
+	xmlStructuredErrorFunc saved_errfunc;
+	void	   *saved_errcxt;
+	/* previous libxml entity handler (saved by pg_xml_init) */
+	xmlExternalEntityLoader saved_entityfunc;
+};
+
+static xmlParserInputPtr xmlPgEntityLoader(const char *URL, const char *ID,
+										   xmlParserCtxtPtr ctxt);
+static void xml_errorHandler(void *data, xmlErrorPtr error);
+static void xml_ereport_by_code(int level, int sqlcode,
+								const char *msg, int errcode);
+static void chopStringInfoNewlines(StringInfo str);
+static void appendStringInfoLineSeparator(StringInfo str);
+
+#ifdef USE_LIBXMLCONTEXT
+
+static MemoryContext LibxmlContext = NULL;
+
+static void xml_memory_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);
+#endif							/* USE_LIBXMLCONTEXT */
+
+static xmlChar *xml_text2xmlChar(text *in);
+static int	parse_xml_decl(const xmlChar *str, size_t *lenp,
+						   xmlChar **version, xmlChar **encoding, int *standalone);
+static bool print_xml_decl(StringInfo buf, const xmlChar *version,
+						   pg_enc encoding, int standalone);
+static bool xml_doctype_in_content(const xmlChar *str);
+static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
+						   bool preserve_whitespace, int encoding);
+static text *xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt);
+static int	xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
+								   ArrayBuildState *astate,
+								   PgXmlErrorContext *xmlerrcxt);
+static xmlChar *pg_xmlCharStrndup(const char *str, size_t len);
+#endif							/* USE_LIBXML */
+
+static void xmldata_root_element_start(StringInfo result, const char *eltname,
+									   const char *xmlschema, const char *targetns,
+									   bool top_level);
+static void xmldata_root_element_end(StringInfo result, const char *eltname);
+static StringInfo query_to_xml_internal(const char *query, char *tablename,
+										const char *xmlschema, bool nulls, bool tableforest,
+										const char *targetns, bool top_level);
+static const char *map_sql_table_to_xmlschema(TupleDesc tupdesc, Oid relid,
+											  bool nulls, bool tableforest, const char *targetns);
+static const char *map_sql_schema_to_xmlschema_types(Oid nspid,
+													 List *relid_list, bool nulls,
+													 bool tableforest, const char *targetns);
+static const char *map_sql_catalog_to_xmlschema_types(List *nspid_list,
+													  bool nulls, bool tableforest,
+													  const char *targetns);
+static const char *map_sql_type_to_xml_name(Oid typeoid, int typmod);
+static const char *map_sql_typecoll_to_xmlschema_types(List *tupdesc_list);
+static const char *map_sql_type_to_xmlschema_type(Oid typeoid, int typmod);
+static void SPI_sql_row_to_xmlelement(uint64 rownum, StringInfo result,
+									  char *tablename, bool nulls, bool tableforest,
+									  const char *targetns, bool top_level);
+
+/* XMLTABLE support */
+#ifdef USE_LIBXML
+/* random number to identify XmlTableContext */
+#define XMLTABLE_CONTEXT_MAGIC	46922182
+typedef struct XmlTableBuilderData
+{
+	int			magic;
+	int			natts;
+	long int	row_count;
+	PgXmlErrorContext *xmlerrcxt;
+	xmlParserCtxtPtr ctxt;
+	xmlDocPtr	doc;
+	xmlXPathContextPtr xpathcxt;
+	xmlXPathCompExprPtr xpathcomp;
+	xmlXPathObjectPtr xpathobj;
+	xmlXPathCompExprPtr *xpathscomp;
+} XmlTableBuilderData;
+#endif
+
+static void XmlTableInitOpaque(struct TableFuncScanState *state, int natts);
+static void XmlTableSetDocument(struct TableFuncScanState *state, Datum value);
+static void XmlTableSetNamespace(struct TableFuncScanState *state, const char *name,
+								 const char *uri);
+static void XmlTableSetRowFilter(struct TableFuncScanState *state, const char *path);
+static void XmlTableSetColumnFilter(struct TableFuncScanState *state,
+									const char *path, int colnum);
+static bool XmlTableFetchRow(struct TableFuncScanState *state);
+static Datum XmlTableGetValue(struct TableFuncScanState *state, int colnum,
+							  Oid typid, int32 typmod, bool *isnull);
+static void XmlTableDestroyOpaque(struct TableFuncScanState *state);
+
+const TableFuncRoutine XmlTableRoutine =
+{
+	XmlTableInitOpaque,
+	XmlTableSetDocument,
+	XmlTableSetNamespace,
+	XmlTableSetRowFilter,
+	XmlTableSetColumnFilter,
+	XmlTableFetchRow,
+	XmlTableGetValue,
+	XmlTableDestroyOpaque
+};
+
+#define NO_XML_SUPPORT() \
+	ereport(ERROR, \
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED), \
+			 errmsg("unsupported XML feature"), \
+			 errdetail("This functionality requires the server to be built with libxml support."), \
+			 errhint("You need to rebuild PostgreSQL using --with-libxml.")))
+
+
+/* from SQL/XML:2008 section 4.9 */
+#define NAMESPACE_XSD "http://www.w3.org/2001/XMLSchema"
+#define NAMESPACE_XSI "http://www.w3.org/2001/XMLSchema-instance"
+#define NAMESPACE_SQLXML "http://standards.iso.org/iso/9075/2003/sqlxml"
+
+
+#ifdef USE_LIBXML
+
+static int
+xmlChar_to_encoding(const xmlChar *encoding_name)
+{
+	int			encoding = pg_char_to_encoding((const char *) encoding_name);
+
+	if (encoding < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid encoding name \"%s\"",
+						(const char *) encoding_name)));
+	return encoding;
+}
+#endif
+
+
+/*
+ * xml_in uses a plain C string to VARDATA conversion, so for the time being
+ * we use the conversion function for the text datatype.
+ *
+ * This is only acceptable so long as xmltype and text use the same
+ * representation.
+ */
+Datum
+xml_in(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	char	   *s = PG_GETARG_CSTRING(0);
+	xmltype    *vardata;
+	xmlDocPtr	doc;
+
+	vardata = (xmltype *) cstring_to_text(s);
+
+	/*
+	 * Parse the data to check if it is well-formed XML data.  Assume that
+	 * ERROR occurred if parsing failed.
+	 */
+	doc = xml_parse(vardata, xmloption, true, GetDatabaseEncoding());
+	xmlFreeDoc(doc);
+
+	PG_RETURN_XML_P(vardata);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+#define PG_XML_DEFAULT_VERSION "1.0"
+
+
+/*
+ * xml_out_internal uses a plain VARDATA to C string conversion, so for the
+ * time being we use the conversion function for the text datatype.
+ *
+ * This is only acceptable so long as xmltype and text use the same
+ * representation.
+ */
+static char *
+xml_out_internal(xmltype *x, pg_enc target_encoding)
+{
+	char	   *str = text_to_cstring((text *) x);
+
+#ifdef USE_LIBXML
+	size_t		len = strlen(str);
+	xmlChar    *version;
+	int			standalone;
+	int			res_code;
+
+	if ((res_code = parse_xml_decl((xmlChar *) str,
+								   &len, &version, NULL, &standalone)) == 0)
+	{
+		StringInfoData buf;
+
+		initStringInfo(&buf);
+
+		if (!print_xml_decl(&buf, version, target_encoding, standalone))
+		{
+			/*
+			 * If we are not going to produce an XML declaration, eat a single
+			 * newline in the original string to prevent empty first lines in
+			 * the output.
+			 */
+			if (*(str + len) == '\n')
+				len += 1;
+		}
+		appendStringInfoString(&buf, str + len);
+
+		pfree(str);
+
+		return buf.data;
+	}
+
+	xml_ereport_by_code(WARNING, ERRCODE_INTERNAL_ERROR,
+						"could not parse XML declaration in stored value",
+						res_code);
+#endif
+	return str;
+}
+
+
+Datum
+xml_out(PG_FUNCTION_ARGS)
+{
+	xmltype    *x = PG_GETARG_XML_P(0);
+
+	/*
+	 * xml_out removes the encoding property in all cases.  This is because we
+	 * cannot control from here whether the datum will be converted to a
+	 * different client encoding, so we'd do more harm than good by including
+	 * it.
+	 */
+	PG_RETURN_CSTRING(xml_out_internal(x, 0));
+}
+
+
+Datum
+xml_recv(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
+	xmltype    *result;
+	char	   *str;
+	char	   *newstr;
+	int			nbytes;
+	xmlDocPtr	doc;
+	xmlChar    *encodingStr = NULL;
+	int			encoding;
+
+	/*
+	 * Read the data in raw format. We don't know yet what the encoding is, as
+	 * that information is embedded in the xml declaration; so we have to
+	 * parse that before converting to server encoding.
+	 */
+	nbytes = buf->len - buf->cursor;
+	str = (char *) pq_getmsgbytes(buf, nbytes);
+
+	/*
+	 * We need a null-terminated string to pass to parse_xml_decl().  Rather
+	 * than make a separate copy, make the temporary result one byte bigger
+	 * than it needs to be.
+	 */
+	result = palloc(nbytes + 1 + VARHDRSZ);
+	SET_VARSIZE(result, nbytes + VARHDRSZ);
+	memcpy(VARDATA(result), str, nbytes);
+	str = VARDATA(result);
+	str[nbytes] = '\0';
+
+	parse_xml_decl((const xmlChar *) str, NULL, NULL, &encodingStr, NULL);
+
+	/*
+	 * If encoding wasn't explicitly specified in the XML header, treat it as
+	 * UTF-8, as that's the default in XML. This is different from xml_in(),
+	 * where the input has to go through the normal client to server encoding
+	 * conversion.
+	 */
+	encoding = encodingStr ? xmlChar_to_encoding(encodingStr) : PG_UTF8;
+
+	/*
+	 * Parse the data to check if it is well-formed XML data.  Assume that
+	 * xml_parse will throw ERROR if not.
+	 */
+	doc = xml_parse(result, xmloption, true, encoding);
+	xmlFreeDoc(doc);
+
+	/* Now that we know what we're dealing with, convert to server encoding */
+	newstr = pg_any_to_server(str, nbytes, encoding);
+
+	if (newstr != str)
+	{
+		pfree(result);
+		result = (xmltype *) cstring_to_text(newstr);
+		pfree(newstr);
+	}
+
+	PG_RETURN_XML_P(result);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+Datum
+xml_send(PG_FUNCTION_ARGS)
+{
+	xmltype    *x = PG_GETARG_XML_P(0);
+	char	   *outval;
+	StringInfoData buf;
+
+	/*
+	 * xml_out_internal doesn't convert the encoding, it just prints the right
+	 * declaration. pq_sendtext will do the conversion.
+	 */
+	outval = xml_out_internal(x, pg_get_client_encoding());
+
+	pq_begintypsend(&buf);
+	pq_sendtext(&buf, outval, strlen(outval));
+	pfree(outval);
+	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
+}
+
+
+#ifdef USE_LIBXML
+static void
+appendStringInfoText(StringInfo str, const text *t)
+{
+	appendBinaryStringInfo(str, VARDATA_ANY(t), VARSIZE_ANY_EXHDR(t));
+}
+#endif
+
+
+static xmltype *
+stringinfo_to_xmltype(StringInfo buf)
+{
+	return (xmltype *) cstring_to_text_with_len(buf->data, buf->len);
+}
+
+
+static xmltype *
+cstring_to_xmltype(const char *string)
+{
+	return (xmltype *) cstring_to_text(string);
+}
+
+
+#ifdef USE_LIBXML
+static xmltype *
+xmlBuffer_to_xmltype(xmlBufferPtr buf)
+{
+	return (xmltype *) cstring_to_text_with_len((const char *) xmlBufferContent(buf),
+												xmlBufferLength(buf));
+}
+#endif
+
+
+Datum
+xmlcomment(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *arg = PG_GETARG_TEXT_PP(0);
+	char	   *argdata = VARDATA_ANY(arg);
+	int			len = VARSIZE_ANY_EXHDR(arg);
+	StringInfoData buf;
+	int			i;
+
+	/* check for "--" in string or "-" at the end */
+	for (i = 1; i < len; i++)
+	{
+		if (argdata[i] == '-' && argdata[i - 1] == '-')
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_XML_COMMENT),
+					 errmsg("invalid XML comment")));
+	}
+	if (len > 0 && argdata[len - 1] == '-')
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_XML_COMMENT),
+				 errmsg("invalid XML comment")));
+
+	initStringInfo(&buf);
+	appendStringInfoString(&buf, "<!--");
+	appendStringInfoText(&buf, arg);
+	appendStringInfoString(&buf, "-->");
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(&buf));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+
+
+/*
+ * TODO: xmlconcat needs to merge the notations and unparsed entities
+ * of the argument values.  Not very important in practice, though.
+ */
+xmltype *
+xmlconcat(List *args)
+{
+#ifdef USE_LIBXML
+	int			global_standalone = 1;
+	xmlChar    *global_version = NULL;
+	bool		global_version_no_value = false;
+	StringInfoData buf;
+	ListCell   *v;
+
+	initStringInfo(&buf);
+	foreach(v, args)
+	{
+		xmltype    *x = DatumGetXmlP(PointerGetDatum(lfirst(v)));
+		size_t		len;
+		xmlChar    *version;
+		int			standalone;
+		char	   *str;
+
+		len = VARSIZE(x) - VARHDRSZ;
+		str = text_to_cstring((text *) x);
+
+		parse_xml_decl((xmlChar *) str, &len, &version, NULL, &standalone);
+
+		if (standalone == 0 && global_standalone == 1)
+			global_standalone = 0;
+		if (standalone < 0)
+			global_standalone = -1;
+
+		if (!version)
+			global_version_no_value = true;
+		else if (!global_version)
+			global_version = version;
+		else if (xmlStrcmp(version, global_version) != 0)
+			global_version_no_value = true;
+
+		appendStringInfoString(&buf, str + len);
+		pfree(str);
+	}
+
+	if (!global_version_no_value || global_standalone >= 0)
+	{
+		StringInfoData buf2;
+
+		initStringInfo(&buf2);
+
+		print_xml_decl(&buf2,
+					   (!global_version_no_value) ? global_version : NULL,
+					   0,
+					   global_standalone);
+
+		appendBinaryStringInfo(&buf2, buf.data, buf.len);
+		buf = buf2;
+	}
+
+	return stringinfo_to_xmltype(&buf);
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
+/*
+ * XMLAGG support
+ */
+Datum
+xmlconcat2(PG_FUNCTION_ARGS)
+{
+	if (PG_ARGISNULL(0))
+	{
+		if (PG_ARGISNULL(1))
+			PG_RETURN_NULL();
+		else
+			PG_RETURN_XML_P(PG_GETARG_XML_P(1));
+	}
+	else if (PG_ARGISNULL(1))
+		PG_RETURN_XML_P(PG_GETARG_XML_P(0));
+	else
+		PG_RETURN_XML_P(xmlconcat(list_make2(PG_GETARG_XML_P(0),
+											 PG_GETARG_XML_P(1))));
+}
+
+
+Datum
+texttoxml(PG_FUNCTION_ARGS)
+{
+	text	   *data = PG_GETARG_TEXT_PP(0);
+
+	PG_RETURN_XML_P(xmlparse(data, xmloption, true));
+}
+
+
+Datum
+xmltotext(PG_FUNCTION_ARGS)
+{
+	xmltype    *data = PG_GETARG_XML_P(0);
+
+	/* It's actually binary compatible. */
+	PG_RETURN_TEXT_P((text *) data);
+}
+
+
+text *
+xmltotext_with_xmloption(xmltype *data, XmlOptionType xmloption_arg)
+{
+	if (xmloption_arg == XMLOPTION_DOCUMENT && !xml_is_document(data))
+		ereport(ERROR,
+				(errcode(ERRCODE_NOT_AN_XML_DOCUMENT),
+				 errmsg("not an XML document")));
+
+	/* It's actually binary compatible, save for the above check. */
+	return (text *) data;
+}
+
+
+xmltype *
+xmlelement(XmlExpr *xexpr,
+		   Datum *named_argvalue, bool *named_argnull,
+		   Datum *argvalue, bool *argnull)
+{
+#ifdef USE_LIBXML
+	xmltype    *result;
+	List	   *named_arg_strings;
+	List	   *arg_strings;
+	int			i;
+	ListCell   *arg;
+	ListCell   *narg;
+	PgXmlErrorContext *xmlerrcxt;
+	volatile xmlBufferPtr buf = NULL;
+	volatile xmlTextWriterPtr writer = NULL;
+
+	/*
+	 * All arguments are already evaluated, and their values are passed in the
+	 * named_argvalue/named_argnull or argvalue/argnull arrays.  This avoids
+	 * issues if one of the arguments involves a call to some other function
+	 * or subsystem that wants to use libxml on its own terms.  We examine the
+	 * original XmlExpr to identify the numbers and types of the arguments.
+	 */
+	named_arg_strings = NIL;
+	i = 0;
+	foreach(arg, xexpr->named_args)
+	{
+		Expr	   *e = (Expr *) lfirst(arg);
+		char	   *str;
+
+		if (named_argnull[i])
+			str = NULL;
+		else
+			str = map_sql_value_to_xml_value(named_argvalue[i],
+											 exprType((Node *) e),
+											 false);
+		named_arg_strings = lappend(named_arg_strings, str);
+		i++;
+	}
+
+	arg_strings = NIL;
+	i = 0;
+	foreach(arg, xexpr->args)
+	{
+		Expr	   *e = (Expr *) lfirst(arg);
+		char	   *str;
+
+		/* here we can just forget NULL elements immediately */
+		if (!argnull[i])
+		{
+			str = map_sql_value_to_xml_value(argvalue[i],
+											 exprType((Node *) e),
+											 true);
+			arg_strings = lappend(arg_strings, str);
+		}
+		i++;
+	}
+
+	xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_ALL);
+
+	PG_TRY();
+	{
+		buf = xmlBufferCreate();
+		if (buf == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate xmlBuffer");
+		writer = xmlNewTextWriterMemory(buf, 0);
+		if (writer == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate xmlTextWriter");
+
+		xmlTextWriterStartElement(writer, (xmlChar *) xexpr->name);
+
+		forboth(arg, named_arg_strings, narg, xexpr->arg_names)
+		{
+			char	   *str = (char *) lfirst(arg);
+			char	   *argname = strVal(lfirst(narg));
+
+			if (str)
+				xmlTextWriterWriteAttribute(writer,
+											(xmlChar *) argname,
+											(xmlChar *) str);
+		}
+
+		foreach(arg, arg_strings)
+		{
+			char	   *str = (char *) lfirst(arg);
+
+			xmlTextWriterWriteRaw(writer, (xmlChar *) str);
+		}
+
+		xmlTextWriterEndElement(writer);
+
+		/* we MUST do this now to flush data out to the buffer ... */
+		xmlFreeTextWriter(writer);
+		writer = NULL;
+
+		result = xmlBuffer_to_xmltype(buf);
+	}
+	PG_CATCH();
+	{
+		if (writer)
+			xmlFreeTextWriter(writer);
+		if (buf)
+			xmlBufferFree(buf);
+
+		pg_xml_done(xmlerrcxt, true);
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	xmlBufferFree(buf);
+
+	pg_xml_done(xmlerrcxt, false);
+
+	return result;
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
+xmltype *
+xmlparse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace)
+{
+#ifdef USE_LIBXML
+	xmlDocPtr	doc;
+
+	doc = xml_parse(data, xmloption_arg, preserve_whitespace,
+					GetDatabaseEncoding());
+	xmlFreeDoc(doc);
+
+	return (xmltype *) data;
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
+xmltype *
+xmlpi(const char *target, text *arg, bool arg_is_null, bool *result_is_null)
+{
+#ifdef USE_LIBXML
+	xmltype    *result;
+	StringInfoData buf;
+
+	if (pg_strcasecmp(target, "xml") == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR), /* really */
+				 errmsg("invalid XML processing instruction"),
+				 errdetail("XML processing instruction target name cannot be \"%s\".", target)));
+
+	/*
+	 * Following the SQL standard, the null check comes after the syntax check
+	 * above.
+	 */
+	*result_is_null = arg_is_null;
+	if (*result_is_null)
+		return NULL;
+
+	initStringInfo(&buf);
+
+	appendStringInfo(&buf, "<?%s", target);
+
+	if (arg != NULL)
+	{
+		char	   *string;
+
+		string = text_to_cstring(arg);
+		if (strstr(string, "?>") != NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_XML_PROCESSING_INSTRUCTION),
+					 errmsg("invalid XML processing instruction"),
+					 errdetail("XML processing instruction cannot contain \"?>\".")));
+
+		appendStringInfoChar(&buf, ' ');
+		appendStringInfoString(&buf, string + strspn(string, " "));
+		pfree(string);
+	}
+	appendStringInfoString(&buf, "?>");
+
+	result = stringinfo_to_xmltype(&buf);
+	pfree(buf.data);
+	return result;
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
+xmltype *
+xmlroot(xmltype *data, text *version, int standalone)
+{
+#ifdef USE_LIBXML
+	char	   *str;
+	size_t		len;
+	xmlChar    *orig_version;
+	int			orig_standalone;
+	StringInfoData buf;
+
+	len = VARSIZE(data) - VARHDRSZ;
+	str = text_to_cstring((text *) data);
+
+	parse_xml_decl((xmlChar *) str, &len, &orig_version, NULL, &orig_standalone);
+
+	if (version)
+		orig_version = xml_text2xmlChar(version);
+	else
+		orig_version = NULL;
+
+	switch (standalone)
+	{
+		case XML_STANDALONE_YES:
+			orig_standalone = 1;
+			break;
+		case XML_STANDALONE_NO:
+			orig_standalone = 0;
+			break;
+		case XML_STANDALONE_NO_VALUE:
+			orig_standalone = -1;
+			break;
+		case XML_STANDALONE_OMITTED:
+			/* leave original value */
+			break;
+	}
+
+	initStringInfo(&buf);
+	print_xml_decl(&buf, orig_version, 0, orig_standalone);
+	appendStringInfoString(&buf, str + len);
+
+	return stringinfo_to_xmltype(&buf);
+#else
+	NO_XML_SUPPORT();
+	return NULL;
+#endif
+}
+
+
+/*
+ * Validate document (given as string) against DTD (given as external link)
+ *
+ * This has been removed because it is a security hole: unprivileged users
+ * should not be able to use Postgres to fetch arbitrary external files,
+ * which unfortunately is exactly what libxml is willing to do with the DTD
+ * parameter.
+ */
+Datum
+xmlvalidate(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("xmlvalidate is not implemented")));
+	return 0;
+}
+
+
+bool
+xml_is_document(xmltype *arg)
+{
+#ifdef USE_LIBXML
+	bool		result;
+	volatile xmlDocPtr doc = NULL;
+	MemoryContext ccxt = CurrentMemoryContext;
+
+	/* We want to catch ereport(INVALID_XML_DOCUMENT) and return false */
+	PG_TRY();
+	{
+		doc = xml_parse((text *) arg, XMLOPTION_DOCUMENT, true,
+						GetDatabaseEncoding());
+		result = true;
+	}
+	PG_CATCH();
+	{
+		ErrorData  *errdata;
+		MemoryContext ecxt;
+
+		ecxt = MemoryContextSwitchTo(ccxt);
+		errdata = CopyErrorData();
+		if (errdata->sqlerrcode == ERRCODE_INVALID_XML_DOCUMENT)
+		{
+			FlushErrorState();
+			result = false;
+		}
+		else
+		{
+			MemoryContextSwitchTo(ecxt);
+			PG_RE_THROW();
+		}
+	}
+	PG_END_TRY();
+
+	if (doc)
+		xmlFreeDoc(doc);
+
+	return result;
+#else							/* not USE_LIBXML */
+	NO_XML_SUPPORT();
+	return false;
+#endif							/* not USE_LIBXML */
+}
+
+
+#ifdef USE_LIBXML
+
+/*
+ * pg_xml_init_library --- set up for use of libxml
+ *
+ * This should be called by each function that is about to use libxml
+ * facilities but doesn't require error handling.  It initializes libxml
+ * and verifies compatibility with the loaded libxml version.  These are
+ * once-per-session activities.
+ *
+ * TODO: xmlChar is utf8-char, make proper tuning (initdb with enc!=utf8 and
+ * check)
+ */
+void
+pg_xml_init_library(void)
+{
+	static bool first_time = true;
+
+	if (first_time)
+	{
+		/* Stuff we need do only once per session */
+
+		/*
+		 * Currently, we have no pure UTF-8 support for internals -- check if
+		 * we can work.
+		 */
+		if (sizeof(char) != sizeof(xmlChar))
+			ereport(ERROR,
+					(errmsg("could not initialize XML library"),
+					 errdetail("libxml2 has incompatible char type: sizeof(char)=%u, sizeof(xmlChar)=%u.",
+							   (int) sizeof(char), (int) sizeof(xmlChar))));
+
+#ifdef USE_LIBXMLCONTEXT
+		/* Set up libxml's memory allocation our way */
+		xml_memory_init();
+#endif
+
+		/* Check library compatibility */
+		LIBXML_TEST_VERSION;
+
+		first_time = false;
+	}
+}
+
+/*
+ * pg_xml_init --- set up for use of libxml and register an error handler
+ *
+ * This should be called by each function that is about to use libxml
+ * facilities and requires error handling.  It initializes libxml with
+ * pg_xml_init_library() and establishes our libxml error handler.
+ *
+ * strictness determines which errors are reported and which are ignored.
+ *
+ * Calls to this function MUST be followed by a PG_TRY block that guarantees
+ * that pg_xml_done() is called during either normal or error exit.
+ *
+ * This is exported for use by contrib/xml2, as well as other code that might
+ * wish to share use of this module's libxml error handler.
+ */
+PgXmlErrorContext *
+pg_xml_init(PgXmlStrictness strictness)
+{
+	PgXmlErrorContext *errcxt;
+	void	   *new_errcxt;
+
+	/* Do one-time setup if needed */
+	pg_xml_init_library();
+
+	/* Create error handling context structure */
+	errcxt = (PgXmlErrorContext *) palloc(sizeof(PgXmlErrorContext));
+	errcxt->magic = ERRCXT_MAGIC;
+	errcxt->strictness = strictness;
+	errcxt->err_occurred = false;
+	initStringInfo(&errcxt->err_buf);
+
+	/*
+	 * Save original error handler and install ours. libxml originally didn't
+	 * distinguish between the contexts for generic and for structured error
+	 * handlers.  If we're using an old libxml version, we must thus save the
+	 * generic error context, even though we're using a structured error
+	 * handler.
+	 */
+	errcxt->saved_errfunc = xmlStructuredError;
+
+#ifdef HAVE_XMLSTRUCTUREDERRORCONTEXT
+	errcxt->saved_errcxt = xmlStructuredErrorContext;
+#else
+	errcxt->saved_errcxt = xmlGenericErrorContext;
+#endif
+
+	xmlSetStructuredErrorFunc((void *) errcxt, xml_errorHandler);
+
+	/*
+	 * Verify that xmlSetStructuredErrorFunc set the context variable we
+	 * expected it to.  If not, the error context pointer we just saved is not
+	 * the correct thing to restore, and since that leaves us without a way to
+	 * restore the context in pg_xml_done, we must fail.
+	 *
+	 * The only known situation in which this test fails is if we compile with
+	 * headers from a libxml2 that doesn't track the structured error context
+	 * separately (< 2.7.4), but at runtime use a version that does, or vice
+	 * versa.  The libxml2 authors did not treat that change as constituting
+	 * an ABI break, so the LIBXML_TEST_VERSION test in pg_xml_init_library
+	 * fails to protect us from this.
+	 */
+
+#ifdef HAVE_XMLSTRUCTUREDERRORCONTEXT
+	new_errcxt = xmlStructuredErrorContext;
+#else
+	new_errcxt = xmlGenericErrorContext;
+#endif
+
+	if (new_errcxt != (void *) errcxt)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("could not set up XML error handler"),
+				 errhint("This probably indicates that the version of libxml2"
+						 " being used is not compatible with the libxml2"
+						 " header files that PostgreSQL was built with.")));
+
+	/*
+	 * Also, install an entity loader to prevent unwanted fetches of external
+	 * files and URLs.
+	 */
+	errcxt->saved_entityfunc = xmlGetExternalEntityLoader();
+	xmlSetExternalEntityLoader(xmlPgEntityLoader);
+
+	return errcxt;
+}
+
+
+/*
+ * pg_xml_done --- restore previous libxml error handling
+ *
+ * Resets libxml's global error-handling state to what it was before
+ * pg_xml_init() was called.
+ *
+ * This routine verifies that all pending errors have been dealt with
+ * (in assert-enabled builds, anyway).
+ */
+void
+pg_xml_done(PgXmlErrorContext *errcxt, bool isError)
+{
+	void	   *cur_errcxt;
+
+	/* An assert seems like enough protection here */
+	Assert(errcxt->magic == ERRCXT_MAGIC);
+
+	/*
+	 * In a normal exit, there should be no un-handled libxml errors.  But we
+	 * shouldn't try to enforce this during error recovery, since the longjmp
+	 * could have been thrown before xml_ereport had a chance to run.
+	 */
+	Assert(!errcxt->err_occurred || isError);
+
+	/*
+	 * Check that libxml's global state is correct, warn if not.  This is a
+	 * real test and not an Assert because it has a higher probability of
+	 * happening.
+	 */
+#ifdef HAVE_XMLSTRUCTUREDERRORCONTEXT
+	cur_errcxt = xmlStructuredErrorContext;
+#else
+	cur_errcxt = xmlGenericErrorContext;
+#endif
+
+	if (cur_errcxt != (void *) errcxt)
+		elog(WARNING, "libxml error handling state is out of sync with xml.c");
+
+	/* Restore the saved handlers */
+	xmlSetStructuredErrorFunc(errcxt->saved_errcxt, errcxt->saved_errfunc);
+	xmlSetExternalEntityLoader(errcxt->saved_entityfunc);
+
+	/*
+	 * Mark the struct as invalid, just in case somebody somehow manages to
+	 * call xml_errorHandler or xml_ereport with it.
+	 */
+	errcxt->magic = 0;
+
+	/* Release memory */
+	pfree(errcxt->err_buf.data);
+	pfree(errcxt);
+}
+
+
+/*
+ * pg_xml_error_occurred() --- test the error flag
+ */
+bool
+pg_xml_error_occurred(PgXmlErrorContext *errcxt)
+{
+	return errcxt->err_occurred;
+}
+
+
+/*
+ * SQL/XML allows storing "XML documents" or "XML content".  "XML
+ * documents" are specified by the XML specification and are parsed
+ * easily by libxml.  "XML content" is specified by SQL/XML as the
+ * production "XMLDecl? content".  But libxml can only parse the
+ * "content" part, so we have to parse the XML declaration ourselves
+ * to complete this.
+ */
+
+#define CHECK_XML_SPACE(p) \
+	do { \
+		if (!xmlIsBlank_ch(*(p))) \
+			return XML_ERR_SPACE_REQUIRED; \
+	} while (0)
+
+#define SKIP_XML_SPACE(p) \
+	while (xmlIsBlank_ch(*(p))) (p)++
+
+/* Letter | Digit | '.' | '-' | '_' | ':' | CombiningChar | Extender */
+/* Beware of multiple evaluations of argument! */
+#define PG_XMLISNAMECHAR(c) \
+	(xmlIsBaseChar_ch(c) || xmlIsIdeographicQ(c) \
+			|| xmlIsDigit_ch(c) \
+			|| c == '.' || c == '-' || c == '_' || c == ':' \
+			|| xmlIsCombiningQ(c) \
+			|| xmlIsExtender_ch(c))
+
+/* pnstrdup, but deal with xmlChar not char; len is measured in xmlChars */
+static xmlChar *
+xml_pnstrdup(const xmlChar *str, size_t len)
+{
+	xmlChar    *result;
+
+	result = (xmlChar *) palloc((len + 1) * sizeof(xmlChar));
+	memcpy(result, str, len * sizeof(xmlChar));
+	result[len] = 0;
+	return result;
+}
+
+/* Ditto, except input is char* */
+static xmlChar *
+pg_xmlCharStrndup(const char *str, size_t len)
+{
+	xmlChar    *result;
+
+	result = (xmlChar *) palloc((len + 1) * sizeof(xmlChar));
+	memcpy(result, str, len);
+	result[len] = '\0';
+
+	return result;
+}
+
+/*
+ * Copy xmlChar string to PostgreSQL-owned memory, freeing the input.
+ *
+ * The input xmlChar is freed regardless of success of the copy.
+ */
+static char *
+xml_pstrdup_and_free(xmlChar *str)
+{
+	char	   *result;
+
+	if (str)
+	{
+		PG_TRY();
+		{
+			result = pstrdup((char *) str);
+		}
+		PG_FINALLY();
+		{
+			xmlFree(str);
+		}
+		PG_END_TRY();
+	}
+	else
+		result = NULL;
+
+	return result;
+}
+
+/*
+ * str is the null-terminated input string.  Remaining arguments are
+ * output arguments; each can be NULL if value is not wanted.
+ * version and encoding are returned as locally-palloc'd strings.
+ * Result is 0 if OK, an error code if not.
+ */
+static int
+parse_xml_decl(const xmlChar *str, size_t *lenp,
+			   xmlChar **version, xmlChar **encoding, int *standalone)
+{
+	const xmlChar *p;
+	const xmlChar *save_p;
+	size_t		len;
+	int			utf8char;
+	int			utf8len;
+
+	/*
+	 * Only initialize libxml.  We don't need error handling here, but we do
+	 * need to make sure libxml is initialized before calling any of its
+	 * functions.  Note that this is safe (and a no-op) if caller has already
+	 * done pg_xml_init().
+	 */
+	pg_xml_init_library();
+
+	/* Initialize output arguments to "not present" */
+	if (version)
+		*version = NULL;
+	if (encoding)
+		*encoding = NULL;
+	if (standalone)
+		*standalone = -1;
+
+	p = str;
+
+	if (xmlStrncmp(p, (xmlChar *) "<?xml", 5) != 0)
+		goto finished;
+
+	/*
+	 * If next char is a name char, it's a PI like <?xml-stylesheet ...?>
+	 * rather than an XMLDecl, so we have done what we came to do and found no
+	 * XMLDecl.
+	 *
+	 * We need an input length value for xmlGetUTF8Char, but there's no need
+	 * to count the whole document size, so use strnlen not strlen.
+	 */
+	utf8len = strnlen((const char *) (p + 5), MAX_MULTIBYTE_CHAR_LEN);
+	utf8char = xmlGetUTF8Char(p + 5, &utf8len);
+	if (PG_XMLISNAMECHAR(utf8char))
+		goto finished;
+
+	p += 5;
+
+	/* version */
+	CHECK_XML_SPACE(p);
+	SKIP_XML_SPACE(p);
+	if (xmlStrncmp(p, (xmlChar *) "version", 7) != 0)
+		return XML_ERR_VERSION_MISSING;
+	p += 7;
+	SKIP_XML_SPACE(p);
+	if (*p != '=')
+		return XML_ERR_VERSION_MISSING;
+	p += 1;
+	SKIP_XML_SPACE(p);
+
+	if (*p == '\'' || *p == '"')
+	{
+		const xmlChar *q;
+
+		q = xmlStrchr(p + 1, *p);
+		if (!q)
+			return XML_ERR_VERSION_MISSING;
+
+		if (version)
+			*version = xml_pnstrdup(p + 1, q - p - 1);
+		p = q + 1;
+	}
+	else
+		return XML_ERR_VERSION_MISSING;
+
+	/* encoding */
+	save_p = p;
+	SKIP_XML_SPACE(p);
+	if (xmlStrncmp(p, (xmlChar *) "encoding", 8) == 0)
+	{
+		CHECK_XML_SPACE(save_p);
+		p += 8;
+		SKIP_XML_SPACE(p);
+		if (*p != '=')
+			return XML_ERR_MISSING_ENCODING;
+		p += 1;
+		SKIP_XML_SPACE(p);
+
+		if (*p == '\'' || *p == '"')
+		{
+			const xmlChar *q;
+
+			q = xmlStrchr(p + 1, *p);
+			if (!q)
+				return XML_ERR_MISSING_ENCODING;
+
+			if (encoding)
+				*encoding = xml_pnstrdup(p + 1, q - p - 1);
+			p = q + 1;
+		}
+		else
+			return XML_ERR_MISSING_ENCODING;
+	}
+	else
+	{
+		p = save_p;
+	}
+
+	/* standalone */
+	save_p = p;
+	SKIP_XML_SPACE(p);
+	if (xmlStrncmp(p, (xmlChar *) "standalone", 10) == 0)
+	{
+		CHECK_XML_SPACE(save_p);
+		p += 10;
+		SKIP_XML_SPACE(p);
+		if (*p != '=')
+			return XML_ERR_STANDALONE_VALUE;
+		p += 1;
+		SKIP_XML_SPACE(p);
+		if (xmlStrncmp(p, (xmlChar *) "'yes'", 5) == 0 ||
+			xmlStrncmp(p, (xmlChar *) "\"yes\"", 5) == 0)
+		{
+			if (standalone)
+				*standalone = 1;
+			p += 5;
+		}
+		else if (xmlStrncmp(p, (xmlChar *) "'no'", 4) == 0 ||
+				 xmlStrncmp(p, (xmlChar *) "\"no\"", 4) == 0)
+		{
+			if (standalone)
+				*standalone = 0;
+			p += 4;
+		}
+		else
+			return XML_ERR_STANDALONE_VALUE;
+	}
+	else
+	{
+		p = save_p;
+	}
+
+	SKIP_XML_SPACE(p);
+	if (xmlStrncmp(p, (xmlChar *) "?>", 2) != 0)
+		return XML_ERR_XMLDECL_NOT_FINISHED;
+	p += 2;
+
+finished:
+	len = p - str;
+
+	for (p = str; p < str + len; p++)
+		if (*p > 127)
+			return XML_ERR_INVALID_CHAR;
+
+	if (lenp)
+		*lenp = len;
+
+	return XML_ERR_OK;
+}
+
+
+/*
+ * Write an XML declaration.  On output, we adjust the XML declaration
+ * as follows.  (These rules are the moral equivalent of the clause
+ * "Serialization of an XML value" in the SQL standard.)
+ *
+ * We try to avoid generating an XML declaration if possible.  This is
+ * so that you don't get trivial things like xml '<foo/>' resulting in
+ * '<?xml version="1.0"?><foo/>', which would surely be annoying.  We
+ * must provide a declaration if the standalone property is specified
+ * or if we include an encoding declaration.  If we have a
+ * declaration, we must specify a version (XML requires this).
+ * Otherwise we only make a declaration if the version is not "1.0",
+ * which is the default version specified in SQL:2003.
+ */
+static bool
+print_xml_decl(StringInfo buf, const xmlChar *version,
+			   pg_enc encoding, int standalone)
+{
+	if ((version && strcmp((const char *) version, PG_XML_DEFAULT_VERSION) != 0)
+		|| (encoding && encoding != PG_UTF8)
+		|| standalone != -1)
+	{
+		appendStringInfoString(buf, "<?xml");
+
+		if (version)
+			appendStringInfo(buf, " version=\"%s\"", version);
+		else
+			appendStringInfo(buf, " version=\"%s\"", PG_XML_DEFAULT_VERSION);
+
+		if (encoding && encoding != PG_UTF8)
+		{
+			/*
+			 * XXX might be useful to convert this to IANA names (ISO-8859-1
+			 * instead of LATIN1 etc.); needs field experience
+			 */
+			appendStringInfo(buf, " encoding=\"%s\"",
+							 pg_encoding_to_char(encoding));
+		}
+
+		if (standalone == 1)
+			appendStringInfoString(buf, " standalone=\"yes\"");
+		else if (standalone == 0)
+			appendStringInfoString(buf, " standalone=\"no\"");
+		appendStringInfoString(buf, "?>");
+
+		return true;
+	}
+	else
+		return false;
+}
+
+/*
+ * Test whether an input that is to be parsed as CONTENT contains a DTD.
+ *
+ * The SQL/XML:2003 definition of CONTENT ("XMLDecl? content") is not
+ * satisfied by a document with a DTD, which is a bit of a wart, as it means
+ * the CONTENT type is not a proper superset of DOCUMENT.  SQL/XML:2006 and
+ * later fix that, by redefining content with reference to the "more
+ * permissive" Document Node of the XQuery/XPath Data Model, such that any
+ * DOCUMENT value is indeed also a CONTENT value.  That definition is more
+ * useful, as CONTENT becomes usable for parsing input of unknown form (think
+ * pg_restore).
+ *
+ * As used below in parse_xml when parsing for CONTENT, libxml does not give
+ * us the 2006+ behavior, but only the 2003; it will choke if the input has
+ * a DTD.  But we can provide the 2006+ definition of CONTENT easily enough,
+ * by detecting this case first and simply doing the parse as DOCUMENT.
+ *
+ * A DTD can be found arbitrarily far in, but that would be a contrived case;
+ * it will ordinarily start within a few dozen characters.  The only things
+ * that can precede it are an XMLDecl (here, the caller will have called
+ * parse_xml_decl already), whitespace, comments, and processing instructions.
+ * This function need only return true if it sees a valid sequence of such
+ * things leading to <!DOCTYPE.  It can simply return false in any other
+ * cases, including malformed input; that will mean the input gets parsed as
+ * CONTENT as originally planned, with libxml reporting any errors.
+ *
+ * This is only to be called from xml_parse, when pg_xml_init has already
+ * been called.  The input is already in UTF8 encoding.
+ */
+static bool
+xml_doctype_in_content(const xmlChar *str)
+{
+	const xmlChar *p = str;
+
+	for (;;)
+	{
+		const xmlChar *e;
+
+		SKIP_XML_SPACE(p);
+		if (*p != '<')
+			return false;
+		p++;
+
+		if (*p == '!')
+		{
+			p++;
+
+			/* if we see <!DOCTYPE, we can return true */
+			if (xmlStrncmp(p, (xmlChar *) "DOCTYPE", 7) == 0)
+				return true;
+
+			/* otherwise, if it's not a comment, fail */
+			if (xmlStrncmp(p, (xmlChar *) "--", 2) != 0)
+				return false;
+			/* find end of comment: find -- and a > must follow */
+			p = xmlStrstr(p + 2, (xmlChar *) "--");
+			if (!p || p[2] != '>')
+				return false;
+			/* advance over comment, and keep scanning */
+			p += 3;
+			continue;
+		}
+
+		/* otherwise, if it's not a PI <?target something?>, fail */
+		if (*p != '?')
+			return false;
+		p++;
+
+		/* find end of PI (the string ?> is forbidden within a PI) */
+		e = xmlStrstr(p, (xmlChar *) "?>");
+		if (!e)
+			return false;
+
+		/* advance over PI, keep scanning */
+		p = e + 2;
+	}
+}
+
+
+/*
+ * Convert a C string to XML internal representation
+ *
+ * Note: it is caller's responsibility to xmlFreeDoc() the result,
+ * else a permanent memory leak will ensue!
+ *
+ * TODO maybe libxml2's xmlreader is better? (do not construct DOM,
+ * yet do not use SAX - see xmlreader.c)
+ */
+static xmlDocPtr
+xml_parse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace,
+		  int encoding)
+{
+	int32		len;
+	xmlChar    *string;
+	xmlChar    *utf8string;
+	PgXmlErrorContext *xmlerrcxt;
+	volatile xmlParserCtxtPtr ctxt = NULL;
+	volatile xmlDocPtr doc = NULL;
+
+	len = VARSIZE_ANY_EXHDR(data);	/* will be useful later */
+	string = xml_text2xmlChar(data);
+
+	utf8string = pg_do_encoding_conversion(string,
+										   len,
+										   encoding,
+										   PG_UTF8);
+
+	/* Start up libxml and its parser */
+	xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_WELLFORMED);
+
+	/* Use a TRY block to ensure we clean up correctly */
+	PG_TRY();
+	{
+		bool		parse_as_document = false;
+		int			res_code;
+		size_t		count = 0;
+		xmlChar    *version = NULL;
+		int			standalone = 0;
+
+		xmlInitParser();
+
+		ctxt = xmlNewParserCtxt();
+		if (ctxt == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate parser context");
+
+		/* Decide whether to parse as document or content */
+		if (xmloption_arg == XMLOPTION_DOCUMENT)
+			parse_as_document = true;
+		else
+		{
+			/* Parse and skip over the XML declaration, if any */
+			res_code = parse_xml_decl(utf8string,
+									  &count, &version, NULL, &standalone);
+			if (res_code != 0)
+				xml_ereport_by_code(ERROR, ERRCODE_INVALID_XML_CONTENT,
+									"invalid XML content: invalid XML declaration",
+									res_code);
+
+			/* Is there a DOCTYPE element? */
+			if (xml_doctype_in_content(utf8string + count))
+				parse_as_document = true;
+		}
+
+		if (parse_as_document)
+		{
+			/*
+			 * Note, that here we try to apply DTD defaults
+			 * (XML_PARSE_DTDATTR) according to SQL/XML:2008 GR 10.16.7.d:
+			 * 'Default values defined by internal DTD are applied'. As for
+			 * external DTDs, we try to support them too, (see SQL/XML:2008 GR
+			 * 10.16.7.e)
+			 */
+			doc = xmlCtxtReadDoc(ctxt, utf8string,
+								 NULL,
+								 "UTF-8",
+								 XML_PARSE_NOENT | XML_PARSE_DTDATTR
+								 | (preserve_whitespace ? 0 : XML_PARSE_NOBLANKS));
+			if (doc == NULL || xmlerrcxt->err_occurred)
+			{
+				/* Use original option to decide which error code to throw */
+				if (xmloption_arg == XMLOPTION_DOCUMENT)
+					xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+								"invalid XML document");
+				else
+					xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_CONTENT,
+								"invalid XML content");
+			}
+		}
+		else
+		{
+			doc = xmlNewDoc(version);
+			Assert(doc->encoding == NULL);
+			doc->encoding = xmlStrdup((const xmlChar *) "UTF-8");
+			doc->standalone = standalone;
+
+			/* allow empty content */
+			if (*(utf8string + count))
+			{
+				res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0,
+													   utf8string + count, NULL);
+				if (res_code != 0 || xmlerrcxt->err_occurred)
+					xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_CONTENT,
+								"invalid XML content");
+			}
+		}
+	}
+	PG_CATCH();
+	{
+		if (doc != NULL)
+			xmlFreeDoc(doc);
+		if (ctxt != NULL)
+			xmlFreeParserCtxt(ctxt);
+
+		pg_xml_done(xmlerrcxt, true);
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	xmlFreeParserCtxt(ctxt);
+
+	pg_xml_done(xmlerrcxt, false);
+
+	return doc;
+}
+
+
+/*
+ * xmlChar<->text conversions
+ */
+static xmlChar *
+xml_text2xmlChar(text *in)
+{
+	return (xmlChar *) text_to_cstring(in);
+}
+
+
+#ifdef USE_LIBXMLCONTEXT
+
+/*
+ * Manage the special context used for all libxml allocations (but only
+ * in special debug builds; see notes at top of file)
+ */
+static void
+xml_memory_init(void)
+{
+	/* Create memory context if not there already */
+	if (LibxmlContext == NULL)
+		LibxmlContext = AllocSetContextCreate(TopMemoryContext,
+											  "Libxml context",
+											  ALLOCSET_DEFAULT_SIZES);
+
+	/* Re-establish the callbacks even if already set */
+	xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
+}
+
+/*
+ * Wrappers for memory management functions
+ */
+static void *
+xml_palloc(size_t size)
+{
+	return MemoryContextAlloc(LibxmlContext, size);
+}
+
+
+static void *
+xml_repalloc(void *ptr, size_t size)
+{
+	return repalloc(ptr, size);
+}
+
+
+static void
+xml_pfree(void *ptr)
+{
+	/* At least some parts of libxml assume xmlFree(NULL) is allowed */
+	if (ptr)
+		pfree(ptr);
+}
+
+
+static char *
+xml_pstrdup(const char *string)
+{
+	return MemoryContextStrdup(LibxmlContext, string);
+}
+#endif							/* USE_LIBXMLCONTEXT */
+
+
+/*
+ * xmlPgEntityLoader --- entity loader callback function
+ *
+ * Silently prevent any external entity URL from being loaded.  We don't want
+ * to throw an error, so instead make the entity appear to expand to an empty
+ * string.
+ *
+ * We would prefer to allow loading entities that exist in the system's
+ * global XML catalog; but the available libxml2 APIs make that a complex
+ * and fragile task.  For now, just shut down all external access.
+ */
+static xmlParserInputPtr
+xmlPgEntityLoader(const char *URL, const char *ID,
+				  xmlParserCtxtPtr ctxt)
+{
+	return xmlNewStringInputStream(ctxt, (const xmlChar *) "");
+}
+
+
+/*
+ * xml_ereport --- report an XML-related error
+ *
+ * The "msg" is the SQL-level message; some can be adopted from the SQL/XML
+ * standard.  This function adds libxml's native error message, if any, as
+ * detail.
+ *
+ * This is exported for modules that want to share the core libxml error
+ * handler.  Note that pg_xml_init() *must* have been called previously.
+ */
+void
+xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode, const char *msg)
+{
+	char	   *detail;
+
+	/* Defend against someone passing us a bogus context struct */
+	if (errcxt->magic != ERRCXT_MAGIC)
+		elog(ERROR, "xml_ereport called with invalid PgXmlErrorContext");
+
+	/* Flag that the current libxml error has been reported */
+	errcxt->err_occurred = false;
+
+	/* Include detail only if we have some text from libxml */
+	if (errcxt->err_buf.len > 0)
+		detail = errcxt->err_buf.data;
+	else
+		detail = NULL;
+
+	ereport(level,
+			(errcode(sqlcode),
+			 errmsg_internal("%s", msg),
+			 detail ? errdetail_internal("%s", detail) : 0));
+}
+
+
+/*
+ * Error handler for libxml errors and warnings
+ */
+static void
+xml_errorHandler(void *data, xmlErrorPtr error)
+{
+	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
+	xmlParserCtxtPtr ctxt = (xmlParserCtxtPtr) error->ctxt;
+	xmlParserInputPtr input = (ctxt != NULL) ? ctxt->input : NULL;
+	xmlNodePtr	node = error->node;
+	const xmlChar *name = (node != NULL &&
+						   node->type == XML_ELEMENT_NODE) ? node->name : NULL;
+	int			domain = error->domain;
+	int			level = error->level;
+	StringInfo	errorBuf;
+
+	/*
+	 * Defend against someone passing us a bogus context struct.
+	 *
+	 * We force a backend exit if this check fails because longjmp'ing out of
+	 * libxml would likely render it unsafe to use further.
+	 */
+	if (xmlerrcxt->magic != ERRCXT_MAGIC)
+		elog(FATAL, "xml_errorHandler called with invalid PgXmlErrorContext");
+
+	/*----------
+	 * Older libxml versions report some errors differently.
+	 * First, some errors were previously reported as coming from the parser
+	 * domain but are now reported as coming from the namespace domain.
+	 * Second, some warnings were upgraded to errors.
+	 * We attempt to compensate for that here.
+	 *----------
+	 */
+	switch (error->code)
+	{
+		case XML_WAR_NS_URI:
+			level = XML_ERR_ERROR;
+			domain = XML_FROM_NAMESPACE;
+			break;
+
+		case XML_ERR_NS_DECL_ERROR:
+		case XML_WAR_NS_URI_RELATIVE:
+		case XML_WAR_NS_COLUMN:
+		case XML_NS_ERR_XML_NAMESPACE:
+		case XML_NS_ERR_UNDEFINED_NAMESPACE:
+		case XML_NS_ERR_QNAME:
+		case XML_NS_ERR_ATTRIBUTE_REDEFINED:
+		case XML_NS_ERR_EMPTY:
+			domain = XML_FROM_NAMESPACE;
+			break;
+	}
+
+	/* Decide whether to act on the error or not */
+	switch (domain)
+	{
+		case XML_FROM_PARSER:
+		case XML_FROM_NONE:
+		case XML_FROM_MEMORY:
+		case XML_FROM_IO:
+
+			/*
+			 * Suppress warnings about undeclared entities.  We need to do
+			 * this to avoid problems due to not loading DTD definitions.
+			 */
+			if (error->code == XML_WAR_UNDECLARED_ENTITY)
+				return;
+
+			/* Otherwise, accept error regardless of the parsing purpose */
+			break;
+
+		default:
+			/* Ignore error if only doing well-formedness check */
+			if (xmlerrcxt->strictness == PG_XML_STRICTNESS_WELLFORMED)
+				return;
+			break;
+	}
+
+	/* Prepare error message in errorBuf */
+	errorBuf = makeStringInfo();
+
+	if (error->line > 0)
+		appendStringInfo(errorBuf, "line %d: ", error->line);
+	if (name != NULL)
+		appendStringInfo(errorBuf, "element %s: ", name);
+	if (error->message != NULL)
+		appendStringInfoString(errorBuf, error->message);
+	else
+		appendStringInfoString(errorBuf, "(no message provided)");
+
+	/*
+	 * Append context information to errorBuf.
+	 *
+	 * xmlParserPrintFileContext() uses libxml's "generic" error handler to
+	 * write the context.  Since we don't want to duplicate libxml
+	 * functionality here, we set up a generic error handler temporarily.
+	 *
+	 * We use appendStringInfo() directly as libxml's generic error handler.
+	 * This should work because it has essentially the same signature as
+	 * libxml expects, namely (void *ptr, const char *msg, ...).
+	 */
+	if (input != NULL)
+	{
+		xmlGenericErrorFunc errFuncSaved = xmlGenericError;
+		void	   *errCtxSaved = xmlGenericErrorContext;
+
+		xmlSetGenericErrorFunc((void *) errorBuf,
+							   (xmlGenericErrorFunc) appendStringInfo);
+
+		/* Add context information to errorBuf */
+		appendStringInfoLineSeparator(errorBuf);
+
+		xmlParserPrintFileContext(input);
+
+		/* Restore generic error func */
+		xmlSetGenericErrorFunc(errCtxSaved, errFuncSaved);
+	}
+
+	/* Get rid of any trailing newlines in errorBuf */
+	chopStringInfoNewlines(errorBuf);
+
+	/*
+	 * Legacy error handling mode.  err_occurred is never set, we just add the
+	 * message to err_buf.  This mode exists because the xml2 contrib module
+	 * uses our error-handling infrastructure, but we don't want to change its
+	 * behaviour since it's deprecated anyway.  This is also why we don't
+	 * distinguish between notices, warnings and errors here --- the old-style
+	 * generic error handler wouldn't have done that either.
+	 */
+	if (xmlerrcxt->strictness == PG_XML_STRICTNESS_LEGACY)
+	{
+		appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data,
+							   errorBuf->len);
+
+		pfree(errorBuf->data);
+		pfree(errorBuf);
+		return;
+	}
+
+	/*
+	 * We don't want to ereport() here because that'd probably leave libxml in
+	 * an inconsistent state.  Instead, we remember the error and ereport()
+	 * from xml_ereport().
+	 *
+	 * Warnings and notices can be reported immediately since they won't cause
+	 * a longjmp() out of libxml.
+	 */
+	if (level >= XML_ERR_ERROR)
+	{
+		appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
+		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data,
+							   errorBuf->len);
+
+		xmlerrcxt->err_occurred = true;
+	}
+	else if (level >= XML_ERR_WARNING)
+	{
+		ereport(WARNING,
+				(errmsg_internal("%s", errorBuf->data)));
+	}
+	else
+	{
+		ereport(NOTICE,
+				(errmsg_internal("%s", errorBuf->data)));
+	}
+
+	pfree(errorBuf->data);
+	pfree(errorBuf);
+}
+
+
+/*
+ * Wrapper for "ereport" function for XML-related errors.  The "msg"
+ * is the SQL-level message; some can be adopted from the SQL/XML
+ * standard.  This function uses "code" to create a textual detail
+ * message.  At the moment, we only need to cover those codes that we
+ * may raise in this file.
+ */
+static void
+xml_ereport_by_code(int level, int sqlcode,
+					const char *msg, int code)
+{
+	const char *det;
+
+	switch (code)
+	{
+		case XML_ERR_INVALID_CHAR:
+			det = gettext_noop("Invalid character value.");
+			break;
+		case XML_ERR_SPACE_REQUIRED:
+			det = gettext_noop("Space required.");
+			break;
+		case XML_ERR_STANDALONE_VALUE:
+			det = gettext_noop("standalone accepts only 'yes' or 'no'.");
+			break;
+		case XML_ERR_VERSION_MISSING:
+			det = gettext_noop("Malformed declaration: missing version.");
+			break;
+		case XML_ERR_MISSING_ENCODING:
+			det = gettext_noop("Missing encoding in text declaration.");
+			break;
+		case XML_ERR_XMLDECL_NOT_FINISHED:
+			det = gettext_noop("Parsing XML declaration: '?>' expected.");
+			break;
+		default:
+			det = gettext_noop("Unrecognized libxml error code: %d.");
+			break;
+	}
+
+	ereport(level,
+			(errcode(sqlcode),
+			 errmsg_internal("%s", msg),
+			 errdetail(det, code)));
+}
+
+
+/*
+ * Remove all trailing newlines from a StringInfo string
+ */
+static void
+chopStringInfoNewlines(StringInfo str)
+{
+	while (str->len > 0 && str->data[str->len - 1] == '\n')
+		str->data[--str->len] = '\0';
+}
+
+
+/*
+ * Append a newline after removing any existing trailing newlines
+ */
+static void
+appendStringInfoLineSeparator(StringInfo str)
+{
+	chopStringInfoNewlines(str);
+	if (str->len > 0)
+		appendStringInfoChar(str, '\n');
+}
+
+
+/*
+ * Convert one char in the current server encoding to a Unicode codepoint.
+ */
+static pg_wchar
+sqlchar_to_unicode(const char *s)
+{
+	char	   *utf8string;
+	pg_wchar	ret[2];			/* need space for trailing zero */
+
+	/* note we're not assuming s is null-terminated */
+	utf8string = pg_server_to_any(s, pg_mblen(s), PG_UTF8);
+
+	pg_encoding_mb2wchar_with_len(PG_UTF8, utf8string, ret,
+								  pg_encoding_mblen(PG_UTF8, utf8string));
+
+	if (utf8string != s)
+		pfree(utf8string);
+
+	return ret[0];
+}
+
+
+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:2008 section 9.1.
+ */
+char *
+map_sql_identifier_to_xml_name(const char *ident, bool fully_escaped,
+							   bool escape_period)
+{
+#ifdef USE_LIBXML
+	StringInfoData buf;
+	const char *p;
+
+	/*
+	 * SQL/XML doesn't make use of this case anywhere, so it's probably a
+	 * mistake.
+	 */
+	Assert(fully_escaped || !escape_period);
+
+	initStringInfo(&buf);
+
+	for (p = ident; *p; p += pg_mblen(p))
+	{
+		if (*p == ':' && (p == ident || fully_escaped))
+			appendStringInfoString(&buf, "_x003A_");
+		else if (*p == '_' && *(p + 1) == 'x')
+			appendStringInfoString(&buf, "_x005F_");
+		else if (fully_escaped && p == ident &&
+				 pg_strncasecmp(p, "xml", 3) == 0)
+		{
+			if (*p == 'x')
+				appendStringInfoString(&buf, "_x0078_");
+			else
+				appendStringInfoString(&buf, "_x0058_");
+		}
+		else if (escape_period && *p == '.')
+			appendStringInfoString(&buf, "_x002E_");
+		else
+		{
+			pg_wchar	u = sqlchar_to_unicode(p);
+
+			if ((p == ident)
+				? !is_valid_xml_namefirst(u)
+				: !is_valid_xml_namechar(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 */
+}
+
+
+/*
+ * Map XML name to SQL identifier; see SQL/XML:2008 section 9.3.
+ */
+char *
+map_xml_name_to_sql_identifier(const char *name)
+{
+	StringInfoData buf;
+	const char *p;
+
+	initStringInfo(&buf);
+
+	for (p = name; *p; p += pg_mblen(p))
+	{
+		if (*p == '_' && *(p + 1) == 'x'
+			&& isxdigit((unsigned char) *(p + 2))
+			&& isxdigit((unsigned char) *(p + 3))
+			&& isxdigit((unsigned char) *(p + 4))
+			&& isxdigit((unsigned char) *(p + 5))
+			&& *(p + 6) == '_')
+		{
+			char		cbuf[MAX_UNICODE_EQUIVALENT_STRING + 1];
+			unsigned int u;
+
+			sscanf(p + 2, "%X", &u);
+			pg_unicode_to_server(u, (unsigned char *) cbuf);
+			appendStringInfoString(&buf, cbuf);
+			p += 6;
+		}
+		else
+			appendBinaryStringInfo(&buf, p, pg_mblen(p));
+	}
+
+	return buf.data;
+}
+
+/*
+ * Map SQL value to XML value; see SQL/XML:2008 section 9.8.
+ *
+ * When xml_escape_strings is true, then certain characters in string
+ * values are replaced by entity references (&lt; etc.), as specified
+ * in SQL/XML:2008 section 9.8 GR 9) a) iii).   This is normally what is
+ * wanted.  The false case is mainly useful when the resulting value
+ * is used with xmlTextWriterWriteAttribute() to write out an
+ * attribute, because that function does the escaping itself.
+ */
+char *
+map_sql_value_to_xml_value(Datum value, Oid type, bool xml_escape_strings)
+{
+	if (type_is_array_domain(type))
+	{
+		ArrayType  *array;
+		Oid			elmtype;
+		int16		elmlen;
+		bool		elmbyval;
+		char		elmalign;
+		int			num_elems;
+		Datum	   *elem_values;
+		bool	   *elem_nulls;
+		StringInfoData buf;
+		int			i;
+
+		array = DatumGetArrayTypeP(value);
+		elmtype = ARR_ELEMTYPE(array);
+		get_typlenbyvalalign(elmtype, &elmlen, &elmbyval, &elmalign);
+
+		deconstruct_array(array, elmtype,
+						  elmlen, elmbyval, elmalign,
+						  &elem_values, &elem_nulls,
+						  &num_elems);
+
+		initStringInfo(&buf);
+
+		for (i = 0; i < num_elems; i++)
+		{
+			if (elem_nulls[i])
+				continue;
+			appendStringInfoString(&buf, "<element>");
+			appendStringInfoString(&buf,
+								   map_sql_value_to_xml_value(elem_values[i],
+															  elmtype, true));
+			appendStringInfoString(&buf, "</element>");
+		}
+
+		pfree(elem_values);
+		pfree(elem_nulls);
+
+		return buf.data;
+	}
+	else
+	{
+		Oid			typeOut;
+		bool		isvarlena;
+		char	   *str;
+
+		/*
+		 * Flatten domains; the special-case treatments below should apply to,
+		 * eg, domains over boolean not just boolean.
+		 */
+		type = getBaseType(type);
+
+		/*
+		 * Special XSD formatting for some data types
+		 */
+		switch (type)
+		{
+			case BOOLOID:
+				if (DatumGetBool(value))
+					return "true";
+				else
+					return "false";
+
+			case DATEOID:
+				{
+					DateADT		date;
+					struct pg_tm tm;
+					char		buf[MAXDATELEN + 1];
+
+					date = DatumGetDateADT(value);
+					/* XSD doesn't support infinite values */
+					if (DATE_NOT_FINITE(date))
+						ereport(ERROR,
+								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+								 errmsg("date out of range"),
+								 errdetail("XML does not support infinite date values.")));
+					j2date(date + POSTGRES_EPOCH_JDATE,
+						   &(tm.tm_year), &(tm.tm_mon), &(tm.tm_mday));
+					EncodeDateOnly(&tm, USE_XSD_DATES, buf);
+
+					return pstrdup(buf);
+				}
+
+			case TIMESTAMPOID:
+				{
+					Timestamp	timestamp;
+					struct pg_tm tm;
+					fsec_t		fsec;
+					char		buf[MAXDATELEN + 1];
+
+					timestamp = DatumGetTimestamp(value);
+
+					/* XSD doesn't support infinite values */
+					if (TIMESTAMP_NOT_FINITE(timestamp))
+						ereport(ERROR,
+								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+								 errmsg("timestamp out of range"),
+								 errdetail("XML does not support infinite timestamp values.")));
+					else if (timestamp2tm(timestamp, NULL, &tm, &fsec, NULL, NULL) == 0)
+						EncodeDateTime(&tm, fsec, false, 0, NULL, USE_XSD_DATES, buf);
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+								 errmsg("timestamp out of range")));
+
+					return pstrdup(buf);
+				}
+
+			case TIMESTAMPTZOID:
+				{
+					TimestampTz timestamp;
+					struct pg_tm tm;
+					int			tz;
+					fsec_t		fsec;
+					const char *tzn = NULL;
+					char		buf[MAXDATELEN + 1];
+
+					timestamp = DatumGetTimestamp(value);
+
+					/* XSD doesn't support infinite values */
+					if (TIMESTAMP_NOT_FINITE(timestamp))
+						ereport(ERROR,
+								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+								 errmsg("timestamp out of range"),
+								 errdetail("XML does not support infinite timestamp values.")));
+					else if (timestamp2tm(timestamp, &tz, &tm, &fsec, &tzn, NULL) == 0)
+						EncodeDateTime(&tm, fsec, true, tz, tzn, USE_XSD_DATES, buf);
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+								 errmsg("timestamp out of range")));
+
+					return pstrdup(buf);
+				}
+
+#ifdef USE_LIBXML
+			case BYTEAOID:
+				{
+					bytea	   *bstr = DatumGetByteaPP(value);
+					PgXmlErrorContext *xmlerrcxt;
+					volatile xmlBufferPtr buf = NULL;
+					volatile xmlTextWriterPtr writer = NULL;
+					char	   *result;
+
+					xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_ALL);
+
+					PG_TRY();
+					{
+						buf = xmlBufferCreate();
+						if (buf == NULL || xmlerrcxt->err_occurred)
+							xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+										"could not allocate xmlBuffer");
+						writer = xmlNewTextWriterMemory(buf, 0);
+						if (writer == NULL || xmlerrcxt->err_occurred)
+							xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+										"could not allocate xmlTextWriter");
+
+						if (xmlbinary == XMLBINARY_BASE64)
+							xmlTextWriterWriteBase64(writer, VARDATA_ANY(bstr),
+													 0, VARSIZE_ANY_EXHDR(bstr));
+						else
+							xmlTextWriterWriteBinHex(writer, VARDATA_ANY(bstr),
+													 0, VARSIZE_ANY_EXHDR(bstr));
+
+						/* we MUST do this now to flush data out to the buffer */
+						xmlFreeTextWriter(writer);
+						writer = NULL;
+
+						result = pstrdup((const char *) xmlBufferContent(buf));
+					}
+					PG_CATCH();
+					{
+						if (writer)
+							xmlFreeTextWriter(writer);
+						if (buf)
+							xmlBufferFree(buf);
+
+						pg_xml_done(xmlerrcxt, true);
+
+						PG_RE_THROW();
+					}
+					PG_END_TRY();
+
+					xmlBufferFree(buf);
+
+					pg_xml_done(xmlerrcxt, false);
+
+					return result;
+				}
+#endif							/* USE_LIBXML */
+
+		}
+
+		/*
+		 * otherwise, just use the type's native text representation
+		 */
+		getTypeOutputInfo(type, &typeOut, &isvarlena);
+		str = OidOutputFunctionCall(typeOut, value);
+
+		/* ... exactly as-is for XML, and when escaping is not wanted */
+		if (type == XMLOID || !xml_escape_strings)
+			return str;
+
+		/* otherwise, translate special characters as needed */
+		return escape_xml(str);
+	}
+}
+
+
+/*
+ * Escape characters in text that have special meanings in XML.
+ *
+ * Returns a palloc'd string.
+ *
+ * NB: this is intentionally not dependent on libxml.
+ */
+char *
+escape_xml(const char *str)
+{
+	StringInfoData buf;
+	const char *p;
+
+	initStringInfo(&buf);
+	for (p = str; *p; p++)
+	{
+		switch (*p)
+		{
+			case '&':
+				appendStringInfoString(&buf, "&amp;");
+				break;
+			case '<':
+				appendStringInfoString(&buf, "&lt;");
+				break;
+			case '>':
+				appendStringInfoString(&buf, "&gt;");
+				break;
+			case '\r':
+				appendStringInfoString(&buf, "&#x0d;");
+				break;
+			default:
+				appendStringInfoCharMacro(&buf, *p);
+				break;
+		}
+	}
+	return buf.data;
+}
+
+
+static char *
+_SPI_strdup(const char *s)
+{
+	size_t		len = strlen(s) + 1;
+	char	   *ret = SPI_palloc(len);
+
+	memcpy(ret, s, len);
+	return ret;
+}
+
+
+/*
+ * SQL to XML mapping functions
+ *
+ * What follows below was at one point intentionally organized so that
+ * you can read along in the SQL/XML standard. The functions are
+ * mostly split up the way the clauses lay out in the standards
+ * document, and the identifiers are also aligned with the standard
+ * text.  Unfortunately, SQL/XML:2006 reordered the clauses
+ * differently than SQL/XML:2003, so the order below doesn't make much
+ * sense anymore.
+ *
+ * There are many things going on there:
+ *
+ * There are two kinds of mappings: Mapping SQL data (table contents)
+ * to XML documents, and mapping SQL structure (the "schema") to XML
+ * Schema.  And there are functions that do both at the same time.
+ *
+ * Then you can map a database, a schema, or a table, each in both
+ * ways.  This breaks down recursively: Mapping a database invokes
+ * mapping schemas, which invokes mapping tables, which invokes
+ * mapping rows, which invokes mapping columns, although you can't
+ * call the last two from the outside.  Because of this, there are a
+ * number of xyz_internal() functions which are to be called both from
+ * the function manager wrapper and from some upper layer in a
+ * recursive call.
+ *
+ * See the documentation about what the common function arguments
+ * nulls, tableforest, and targetns mean.
+ *
+ * Some style guidelines for XML output: Use double quotes for quoting
+ * XML attributes.  Indent XML elements by two spaces, but remember
+ * that a lot of code is called recursively at different levels, so
+ * it's better not to indent rather than create output that indents
+ * and outdents weirdly.  Add newlines to make the output look nice.
+ */
+
+
+/*
+ * Visibility of objects for XML mappings; see SQL/XML:2008 section
+ * 4.10.8.
+ */
+
+/*
+ * Given a query, which must return type oid as first column, produce
+ * a list of Oids with the query results.
+ */
+static List *
+query_to_oid_list(const char *query)
+{
+	uint64		i;
+	List	   *list = NIL;
+	int			spi_result;
+
+	spi_result = SPI_execute(query, true, 0);
+	if (spi_result != SPI_OK_SELECT)
+		elog(ERROR, "SPI_execute returned %s for %s",
+			 SPI_result_code_string(spi_result), query);
+
+	for (i = 0; i < SPI_processed; i++)
+	{
+		Datum		oid;
+		bool		isnull;
+
+		oid = SPI_getbinval(SPI_tuptable->vals[i],
+							SPI_tuptable->tupdesc,
+							1,
+							&isnull);
+		if (!isnull)
+			list = lappend_oid(list, DatumGetObjectId(oid));
+	}
+
+	return list;
+}
+
+
+static List *
+schema_get_xml_visible_tables(Oid nspid)
+{
+	StringInfoData query;
+
+	initStringInfo(&query);
+	appendStringInfo(&query, "SELECT oid FROM pg_catalog.pg_class"
+					 " WHERE relnamespace = %u AND relkind IN ("
+					 CppAsString2(RELKIND_RELATION) ","
+					 CppAsString2(RELKIND_MATVIEW) ","
+					 CppAsString2(RELKIND_VIEW) ")"
+					 " AND pg_catalog.has_table_privilege (oid, 'SELECT')"
+					 " ORDER BY relname;", nspid);
+
+	return query_to_oid_list(query.data);
+}
+
+
+/*
+ * Including the system schemas is probably not useful for a database
+ * mapping.
+ */
+#define XML_VISIBLE_SCHEMAS_EXCLUDE "(nspname ~ '^pg_' OR nspname = 'information_schema')"
+
+#define XML_VISIBLE_SCHEMAS "SELECT oid FROM pg_catalog.pg_namespace WHERE pg_catalog.has_schema_privilege (oid, 'USAGE') AND NOT " XML_VISIBLE_SCHEMAS_EXCLUDE
+
+
+static List *
+database_get_xml_visible_schemas(void)
+{
+	return query_to_oid_list(XML_VISIBLE_SCHEMAS " ORDER BY nspname;");
+}
+
+
+static List *
+database_get_xml_visible_tables(void)
+{
+	/* At the moment there is no order required here. */
+	return query_to_oid_list("SELECT oid FROM pg_catalog.pg_class"
+							 " WHERE relkind IN ("
+							 CppAsString2(RELKIND_RELATION) ","
+							 CppAsString2(RELKIND_MATVIEW) ","
+							 CppAsString2(RELKIND_VIEW) ")"
+							 " AND pg_catalog.has_table_privilege(pg_class.oid, 'SELECT')"
+							 " AND relnamespace IN (" XML_VISIBLE_SCHEMAS ");");
+}
+
+
+/*
+ * Map SQL table to XML and/or XML Schema document; see SQL/XML:2008
+ * section 9.11.
+ */
+
+static StringInfo
+table_to_xml_internal(Oid relid,
+					  const char *xmlschema, bool nulls, bool tableforest,
+					  const char *targetns, bool top_level)
+{
+	StringInfoData query;
+
+	initStringInfo(&query);
+	appendStringInfo(&query, "SELECT * FROM %s",
+					 DatumGetCString(DirectFunctionCall1(regclassout,
+														 ObjectIdGetDatum(relid))));
+	return query_to_xml_internal(query.data, get_rel_name(relid),
+								 xmlschema, nulls, tableforest,
+								 targetns, top_level);
+}
+
+
+Datum
+table_to_xml(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(table_to_xml_internal(relid, NULL,
+																nulls, tableforest,
+																targetns, true)));
+}
+
+
+Datum
+query_to_xml(PG_FUNCTION_ARGS)
+{
+	char	   *query = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(query_to_xml_internal(query, NULL,
+																NULL, nulls, tableforest,
+																targetns, true)));
+}
+
+
+Datum
+cursor_to_xml(PG_FUNCTION_ARGS)
+{
+	char	   *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	int32		count = PG_GETARG_INT32(1);
+	bool		nulls = PG_GETARG_BOOL(2);
+	bool		tableforest = PG_GETARG_BOOL(3);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(4));
+
+	StringInfoData result;
+	Portal		portal;
+	uint64		i;
+
+	initStringInfo(&result);
+
+	if (!tableforest)
+	{
+		xmldata_root_element_start(&result, "table", NULL, targetns, true);
+		appendStringInfoChar(&result, '\n');
+	}
+
+	SPI_connect();
+	portal = SPI_cursor_find(name);
+	if (portal == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_CURSOR),
+				 errmsg("cursor \"%s\" does not exist", name)));
+
+	SPI_cursor_fetch(portal, true, count);
+	for (i = 0; i < SPI_processed; i++)
+		SPI_sql_row_to_xmlelement(i, &result, NULL, nulls,
+								  tableforest, targetns, true);
+
+	SPI_finish();
+
+	if (!tableforest)
+		xmldata_root_element_end(&result, "table");
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(&result));
+}
+
+
+/*
+ * Write the start tag of the root element of a data mapping.
+ *
+ * top_level means that this is the very top level of the eventual
+ * output.  For example, when the user calls table_to_xml, then a call
+ * with a table name to this function is the top level.  When the user
+ * calls database_to_xml, then a call with a schema name to this
+ * function is not the top level.  If top_level is false, then the XML
+ * namespace declarations are omitted, because they supposedly already
+ * appeared earlier in the output.  Repeating them is not wrong, but
+ * it looks ugly.
+ */
+static void
+xmldata_root_element_start(StringInfo result, const char *eltname,
+						   const char *xmlschema, const char *targetns,
+						   bool top_level)
+{
+	/* This isn't really wrong but currently makes no sense. */
+	Assert(top_level || !xmlschema);
+
+	appendStringInfo(result, "<%s", eltname);
+	if (top_level)
+	{
+		appendStringInfoString(result, " xmlns:xsi=\"" NAMESPACE_XSI "\"");
+		if (strlen(targetns) > 0)
+			appendStringInfo(result, " xmlns=\"%s\"", targetns);
+	}
+	if (xmlschema)
+	{
+		/* FIXME: better targets */
+		if (strlen(targetns) > 0)
+			appendStringInfo(result, " xsi:schemaLocation=\"%s #\"", targetns);
+		else
+			appendStringInfoString(result, " xsi:noNamespaceSchemaLocation=\"#\"");
+	}
+	appendStringInfoString(result, ">\n");
+}
+
+
+static void
+xmldata_root_element_end(StringInfo result, const char *eltname)
+{
+	appendStringInfo(result, "</%s>\n", eltname);
+}
+
+
+static StringInfo
+query_to_xml_internal(const char *query, char *tablename,
+					  const char *xmlschema, bool nulls, bool tableforest,
+					  const char *targetns, bool top_level)
+{
+	StringInfo	result;
+	char	   *xmltn;
+	uint64		i;
+
+	if (tablename)
+		xmltn = map_sql_identifier_to_xml_name(tablename, true, false);
+	else
+		xmltn = "table";
+
+	result = makeStringInfo();
+
+	SPI_connect();
+	if (SPI_execute(query, true, 0) != SPI_OK_SELECT)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_EXCEPTION),
+				 errmsg("invalid query")));
+
+	if (!tableforest)
+	{
+		xmldata_root_element_start(result, xmltn, xmlschema,
+								   targetns, top_level);
+		appendStringInfoChar(result, '\n');
+	}
+
+	if (xmlschema)
+		appendStringInfo(result, "%s\n\n", xmlschema);
+
+	for (i = 0; i < SPI_processed; i++)
+		SPI_sql_row_to_xmlelement(i, result, tablename, nulls,
+								  tableforest, targetns, top_level);
+
+	if (!tableforest)
+		xmldata_root_element_end(result, xmltn);
+
+	SPI_finish();
+
+	return result;
+}
+
+
+Datum
+table_to_xmlschema(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+	const char *result;
+	Relation	rel;
+
+	rel = table_open(relid, AccessShareLock);
+	result = map_sql_table_to_xmlschema(rel->rd_att, relid, nulls,
+										tableforest, targetns);
+	table_close(rel, NoLock);
+
+	PG_RETURN_XML_P(cstring_to_xmltype(result));
+}
+
+
+Datum
+query_to_xmlschema(PG_FUNCTION_ARGS)
+{
+	char	   *query = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+	const char *result;
+	SPIPlanPtr	plan;
+	Portal		portal;
+
+	SPI_connect();
+
+	if ((plan = SPI_prepare(query, 0, NULL)) == NULL)
+		elog(ERROR, "SPI_prepare(\"%s\") failed", query);
+
+	if ((portal = SPI_cursor_open(NULL, plan, NULL, NULL, true)) == NULL)
+		elog(ERROR, "SPI_cursor_open(\"%s\") failed", query);
+
+	result = _SPI_strdup(map_sql_table_to_xmlschema(portal->tupDesc,
+													InvalidOid, nulls,
+													tableforest, targetns));
+	SPI_cursor_close(portal);
+	SPI_finish();
+
+	PG_RETURN_XML_P(cstring_to_xmltype(result));
+}
+
+
+Datum
+cursor_to_xmlschema(PG_FUNCTION_ARGS)
+{
+	char	   *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+	const char *xmlschema;
+	Portal		portal;
+
+	SPI_connect();
+	portal = SPI_cursor_find(name);
+	if (portal == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_CURSOR),
+				 errmsg("cursor \"%s\" does not exist", name)));
+
+	xmlschema = _SPI_strdup(map_sql_table_to_xmlschema(portal->tupDesc,
+													   InvalidOid, nulls,
+													   tableforest, targetns));
+	SPI_finish();
+
+	PG_RETURN_XML_P(cstring_to_xmltype(xmlschema));
+}
+
+
+Datum
+table_to_xml_and_xmlschema(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+	Relation	rel;
+	const char *xmlschema;
+
+	rel = table_open(relid, AccessShareLock);
+	xmlschema = map_sql_table_to_xmlschema(rel->rd_att, relid, nulls,
+										   tableforest, targetns);
+	table_close(rel, NoLock);
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(table_to_xml_internal(relid,
+																xmlschema, nulls, tableforest,
+																targetns, true)));
+}
+
+
+Datum
+query_to_xml_and_xmlschema(PG_FUNCTION_ARGS)
+{
+	char	   *query = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+
+	const char *xmlschema;
+	SPIPlanPtr	plan;
+	Portal		portal;
+
+	SPI_connect();
+
+	if ((plan = SPI_prepare(query, 0, NULL)) == NULL)
+		elog(ERROR, "SPI_prepare(\"%s\") failed", query);
+
+	if ((portal = SPI_cursor_open(NULL, plan, NULL, NULL, true)) == NULL)
+		elog(ERROR, "SPI_cursor_open(\"%s\") failed", query);
+
+	xmlschema = _SPI_strdup(map_sql_table_to_xmlschema(portal->tupDesc,
+													   InvalidOid, nulls, tableforest, targetns));
+	SPI_cursor_close(portal);
+	SPI_finish();
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(query_to_xml_internal(query, NULL,
+																xmlschema, nulls, tableforest,
+																targetns, true)));
+}
+
+
+/*
+ * Map SQL schema to XML and/or XML Schema document; see SQL/XML:2008
+ * sections 9.13, 9.14.
+ */
+
+static StringInfo
+schema_to_xml_internal(Oid nspid, const char *xmlschema, bool nulls,
+					   bool tableforest, const char *targetns, bool top_level)
+{
+	StringInfo	result;
+	char	   *xmlsn;
+	List	   *relid_list;
+	ListCell   *cell;
+
+	xmlsn = map_sql_identifier_to_xml_name(get_namespace_name(nspid),
+										   true, false);
+	result = makeStringInfo();
+
+	xmldata_root_element_start(result, xmlsn, xmlschema, targetns, top_level);
+	appendStringInfoChar(result, '\n');
+
+	if (xmlschema)
+		appendStringInfo(result, "%s\n\n", xmlschema);
+
+	SPI_connect();
+
+	relid_list = schema_get_xml_visible_tables(nspid);
+
+	foreach(cell, relid_list)
+	{
+		Oid			relid = lfirst_oid(cell);
+		StringInfo	subres;
+
+		subres = table_to_xml_internal(relid, NULL, nulls, tableforest,
+									   targetns, false);
+
+		appendBinaryStringInfo(result, subres->data, subres->len);
+		appendStringInfoChar(result, '\n');
+	}
+
+	SPI_finish();
+
+	xmldata_root_element_end(result, xmlsn);
+
+	return result;
+}
+
+
+Datum
+schema_to_xml(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+
+	char	   *schemaname;
+	Oid			nspid;
+
+	schemaname = NameStr(*name);
+	nspid = LookupExplicitNamespace(schemaname, false);
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(schema_to_xml_internal(nspid, NULL,
+																 nulls, tableforest, targetns, true)));
+}
+
+
+/*
+ * Write the start element of the root element of an XML Schema mapping.
+ */
+static void
+xsd_schema_element_start(StringInfo result, const char *targetns)
+{
+	appendStringInfoString(result,
+						   "<xsd:schema\n"
+						   "    xmlns:xsd=\"" NAMESPACE_XSD "\"");
+	if (strlen(targetns) > 0)
+		appendStringInfo(result,
+						 "\n"
+						 "    targetNamespace=\"%s\"\n"
+						 "    elementFormDefault=\"qualified\"",
+						 targetns);
+	appendStringInfoString(result,
+						   ">\n\n");
+}
+
+
+static void
+xsd_schema_element_end(StringInfo result)
+{
+	appendStringInfoString(result, "</xsd:schema>");
+}
+
+
+static StringInfo
+schema_to_xmlschema_internal(const char *schemaname, bool nulls,
+							 bool tableforest, const char *targetns)
+{
+	Oid			nspid;
+	List	   *relid_list;
+	List	   *tupdesc_list;
+	ListCell   *cell;
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	nspid = LookupExplicitNamespace(schemaname, false);
+
+	xsd_schema_element_start(result, targetns);
+
+	SPI_connect();
+
+	relid_list = schema_get_xml_visible_tables(nspid);
+
+	tupdesc_list = NIL;
+	foreach(cell, relid_list)
+	{
+		Relation	rel;
+
+		rel = table_open(lfirst_oid(cell), AccessShareLock);
+		tupdesc_list = lappend(tupdesc_list, CreateTupleDescCopy(rel->rd_att));
+		table_close(rel, NoLock);
+	}
+
+	appendStringInfoString(result,
+						   map_sql_typecoll_to_xmlschema_types(tupdesc_list));
+
+	appendStringInfoString(result,
+						   map_sql_schema_to_xmlschema_types(nspid, relid_list,
+															 nulls, tableforest, targetns));
+
+	xsd_schema_element_end(result);
+
+	SPI_finish();
+
+	return result;
+}
+
+
+Datum
+schema_to_xmlschema(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(schema_to_xmlschema_internal(NameStr(*name),
+																	   nulls, tableforest, targetns)));
+}
+
+
+Datum
+schema_to_xml_and_xmlschema(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+	bool		nulls = PG_GETARG_BOOL(1);
+	bool		tableforest = PG_GETARG_BOOL(2);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(3));
+	char	   *schemaname;
+	Oid			nspid;
+	StringInfo	xmlschema;
+
+	schemaname = NameStr(*name);
+	nspid = LookupExplicitNamespace(schemaname, false);
+
+	xmlschema = schema_to_xmlschema_internal(schemaname, nulls,
+											 tableforest, targetns);
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(schema_to_xml_internal(nspid,
+																 xmlschema->data, nulls,
+																 tableforest, targetns, true)));
+}
+
+
+/*
+ * Map SQL database to XML and/or XML Schema document; see SQL/XML:2008
+ * sections 9.16, 9.17.
+ */
+
+static StringInfo
+database_to_xml_internal(const char *xmlschema, bool nulls,
+						 bool tableforest, const char *targetns)
+{
+	StringInfo	result;
+	List	   *nspid_list;
+	ListCell   *cell;
+	char	   *xmlcn;
+
+	xmlcn = map_sql_identifier_to_xml_name(get_database_name(MyDatabaseId),
+										   true, false);
+	result = makeStringInfo();
+
+	xmldata_root_element_start(result, xmlcn, xmlschema, targetns, true);
+	appendStringInfoChar(result, '\n');
+
+	if (xmlschema)
+		appendStringInfo(result, "%s\n\n", xmlschema);
+
+	SPI_connect();
+
+	nspid_list = database_get_xml_visible_schemas();
+
+	foreach(cell, nspid_list)
+	{
+		Oid			nspid = lfirst_oid(cell);
+		StringInfo	subres;
+
+		subres = schema_to_xml_internal(nspid, NULL, nulls,
+										tableforest, targetns, false);
+
+		appendBinaryStringInfo(result, subres->data, subres->len);
+		appendStringInfoChar(result, '\n');
+	}
+
+	SPI_finish();
+
+	xmldata_root_element_end(result, xmlcn);
+
+	return result;
+}
+
+
+Datum
+database_to_xml(PG_FUNCTION_ARGS)
+{
+	bool		nulls = PG_GETARG_BOOL(0);
+	bool		tableforest = PG_GETARG_BOOL(1);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(2));
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(database_to_xml_internal(NULL, nulls,
+																   tableforest, targetns)));
+}
+
+
+static StringInfo
+database_to_xmlschema_internal(bool nulls, bool tableforest,
+							   const char *targetns)
+{
+	List	   *relid_list;
+	List	   *nspid_list;
+	List	   *tupdesc_list;
+	ListCell   *cell;
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	xsd_schema_element_start(result, targetns);
+
+	SPI_connect();
+
+	relid_list = database_get_xml_visible_tables();
+	nspid_list = database_get_xml_visible_schemas();
+
+	tupdesc_list = NIL;
+	foreach(cell, relid_list)
+	{
+		Relation	rel;
+
+		rel = table_open(lfirst_oid(cell), AccessShareLock);
+		tupdesc_list = lappend(tupdesc_list, CreateTupleDescCopy(rel->rd_att));
+		table_close(rel, NoLock);
+	}
+
+	appendStringInfoString(result,
+						   map_sql_typecoll_to_xmlschema_types(tupdesc_list));
+
+	appendStringInfoString(result,
+						   map_sql_catalog_to_xmlschema_types(nspid_list, nulls, tableforest, targetns));
+
+	xsd_schema_element_end(result);
+
+	SPI_finish();
+
+	return result;
+}
+
+
+Datum
+database_to_xmlschema(PG_FUNCTION_ARGS)
+{
+	bool		nulls = PG_GETARG_BOOL(0);
+	bool		tableforest = PG_GETARG_BOOL(1);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(2));
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(database_to_xmlschema_internal(nulls,
+																		 tableforest, targetns)));
+}
+
+
+Datum
+database_to_xml_and_xmlschema(PG_FUNCTION_ARGS)
+{
+	bool		nulls = PG_GETARG_BOOL(0);
+	bool		tableforest = PG_GETARG_BOOL(1);
+	const char *targetns = text_to_cstring(PG_GETARG_TEXT_PP(2));
+	StringInfo	xmlschema;
+
+	xmlschema = database_to_xmlschema_internal(nulls, tableforest, targetns);
+
+	PG_RETURN_XML_P(stringinfo_to_xmltype(database_to_xml_internal(xmlschema->data,
+																   nulls, tableforest, targetns)));
+}
+
+
+/*
+ * Map a multi-part SQL name to an XML name; see SQL/XML:2008 section
+ * 9.2.
+ */
+static char *
+map_multipart_sql_identifier_to_xml_name(const char *a, const char *b, const char *c, const char *d)
+{
+	StringInfoData result;
+
+	initStringInfo(&result);
+
+	if (a)
+		appendStringInfoString(&result,
+							   map_sql_identifier_to_xml_name(a, true, true));
+	if (b)
+		appendStringInfo(&result, ".%s",
+						 map_sql_identifier_to_xml_name(b, true, true));
+	if (c)
+		appendStringInfo(&result, ".%s",
+						 map_sql_identifier_to_xml_name(c, true, true));
+	if (d)
+		appendStringInfo(&result, ".%s",
+						 map_sql_identifier_to_xml_name(d, true, true));
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL table to an XML Schema document; see SQL/XML:2008
+ * section 9.11.
+ *
+ * Map an SQL table to XML Schema data types; see SQL/XML:2008 section
+ * 9.9.
+ */
+static const char *
+map_sql_table_to_xmlschema(TupleDesc tupdesc, Oid relid, bool nulls,
+						   bool tableforest, const char *targetns)
+{
+	int			i;
+	char	   *xmltn;
+	char	   *tabletypename;
+	char	   *rowtypename;
+	StringInfoData result;
+
+	initStringInfo(&result);
+
+	if (OidIsValid(relid))
+	{
+		HeapTuple	tuple;
+		Form_pg_class reltuple;
+
+		tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
+		if (!HeapTupleIsValid(tuple))
+			elog(ERROR, "cache lookup failed for relation %u", relid);
+		reltuple = (Form_pg_class) GETSTRUCT(tuple);
+
+		xmltn = map_sql_identifier_to_xml_name(NameStr(reltuple->relname),
+											   true, false);
+
+		tabletypename = map_multipart_sql_identifier_to_xml_name("TableType",
+																 get_database_name(MyDatabaseId),
+																 get_namespace_name(reltuple->relnamespace),
+																 NameStr(reltuple->relname));
+
+		rowtypename = map_multipart_sql_identifier_to_xml_name("RowType",
+															   get_database_name(MyDatabaseId),
+															   get_namespace_name(reltuple->relnamespace),
+															   NameStr(reltuple->relname));
+
+		ReleaseSysCache(tuple);
+	}
+	else
+	{
+		if (tableforest)
+			xmltn = "row";
+		else
+			xmltn = "table";
+
+		tabletypename = "TableType";
+		rowtypename = "RowType";
+	}
+
+	xsd_schema_element_start(&result, targetns);
+
+	appendStringInfoString(&result,
+						   map_sql_typecoll_to_xmlschema_types(list_make1(tupdesc)));
+
+	appendStringInfo(&result,
+					 "<xsd:complexType name=\"%s\">\n"
+					 "  <xsd:sequence>\n",
+					 rowtypename);
+
+	for (i = 0; i < tupdesc->natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(tupdesc, i);
+
+		if (att->attisdropped)
+			continue;
+		appendStringInfo(&result,
+						 "    <xsd:element name=\"%s\" type=\"%s\"%s></xsd:element>\n",
+						 map_sql_identifier_to_xml_name(NameStr(att->attname),
+														true, false),
+						 map_sql_type_to_xml_name(att->atttypid, -1),
+						 nulls ? " nillable=\"true\"" : " minOccurs=\"0\"");
+	}
+
+	appendStringInfoString(&result,
+						   "  </xsd:sequence>\n"
+						   "</xsd:complexType>\n\n");
+
+	if (!tableforest)
+	{
+		appendStringInfo(&result,
+						 "<xsd:complexType name=\"%s\">\n"
+						 "  <xsd:sequence>\n"
+						 "    <xsd:element name=\"row\" type=\"%s\" minOccurs=\"0\" maxOccurs=\"unbounded\"/>\n"
+						 "  </xsd:sequence>\n"
+						 "</xsd:complexType>\n\n",
+						 tabletypename, rowtypename);
+
+		appendStringInfo(&result,
+						 "<xsd:element name=\"%s\" type=\"%s\"/>\n\n",
+						 xmltn, tabletypename);
+	}
+	else
+		appendStringInfo(&result,
+						 "<xsd:element name=\"%s\" type=\"%s\"/>\n\n",
+						 xmltn, rowtypename);
+
+	xsd_schema_element_end(&result);
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL schema to XML Schema data types; see SQL/XML:2008
+ * section 9.12.
+ */
+static const char *
+map_sql_schema_to_xmlschema_types(Oid nspid, List *relid_list, bool nulls,
+								  bool tableforest, const char *targetns)
+{
+	char	   *dbname;
+	char	   *nspname;
+	char	   *xmlsn;
+	char	   *schematypename;
+	StringInfoData result;
+	ListCell   *cell;
+
+	dbname = get_database_name(MyDatabaseId);
+	nspname = get_namespace_name(nspid);
+
+	initStringInfo(&result);
+
+	xmlsn = map_sql_identifier_to_xml_name(nspname, true, false);
+
+	schematypename = map_multipart_sql_identifier_to_xml_name("SchemaType",
+															  dbname,
+															  nspname,
+															  NULL);
+
+	appendStringInfo(&result,
+					 "<xsd:complexType name=\"%s\">\n", schematypename);
+	if (!tableforest)
+		appendStringInfoString(&result,
+							   "  <xsd:all>\n");
+	else
+		appendStringInfoString(&result,
+							   "  <xsd:sequence>\n");
+
+	foreach(cell, relid_list)
+	{
+		Oid			relid = lfirst_oid(cell);
+		char	   *relname = get_rel_name(relid);
+		char	   *xmltn = map_sql_identifier_to_xml_name(relname, true, false);
+		char	   *tabletypename = map_multipart_sql_identifier_to_xml_name(tableforest ? "RowType" : "TableType",
+																			 dbname,
+																			 nspname,
+																			 relname);
+
+		if (!tableforest)
+			appendStringInfo(&result,
+							 "    <xsd:element name=\"%s\" type=\"%s\"/>\n",
+							 xmltn, tabletypename);
+		else
+			appendStringInfo(&result,
+							 "    <xsd:element name=\"%s\" type=\"%s\" minOccurs=\"0\" maxOccurs=\"unbounded\"/>\n",
+							 xmltn, tabletypename);
+	}
+
+	if (!tableforest)
+		appendStringInfoString(&result,
+							   "  </xsd:all>\n");
+	else
+		appendStringInfoString(&result,
+							   "  </xsd:sequence>\n");
+	appendStringInfoString(&result,
+						   "</xsd:complexType>\n\n");
+
+	appendStringInfo(&result,
+					 "<xsd:element name=\"%s\" type=\"%s\"/>\n\n",
+					 xmlsn, schematypename);
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL catalog to XML Schema data types; see SQL/XML:2008
+ * section 9.15.
+ */
+static const char *
+map_sql_catalog_to_xmlschema_types(List *nspid_list, bool nulls,
+								   bool tableforest, const char *targetns)
+{
+	char	   *dbname;
+	char	   *xmlcn;
+	char	   *catalogtypename;
+	StringInfoData result;
+	ListCell   *cell;
+
+	dbname = get_database_name(MyDatabaseId);
+
+	initStringInfo(&result);
+
+	xmlcn = map_sql_identifier_to_xml_name(dbname, true, false);
+
+	catalogtypename = map_multipart_sql_identifier_to_xml_name("CatalogType",
+															   dbname,
+															   NULL,
+															   NULL);
+
+	appendStringInfo(&result,
+					 "<xsd:complexType name=\"%s\">\n", catalogtypename);
+	appendStringInfoString(&result,
+						   "  <xsd:all>\n");
+
+	foreach(cell, nspid_list)
+	{
+		Oid			nspid = lfirst_oid(cell);
+		char	   *nspname = get_namespace_name(nspid);
+		char	   *xmlsn = map_sql_identifier_to_xml_name(nspname, true, false);
+		char	   *schematypename = map_multipart_sql_identifier_to_xml_name("SchemaType",
+																			  dbname,
+																			  nspname,
+																			  NULL);
+
+		appendStringInfo(&result,
+						 "    <xsd:element name=\"%s\" type=\"%s\"/>\n",
+						 xmlsn, schematypename);
+	}
+
+	appendStringInfoString(&result,
+						   "  </xsd:all>\n");
+	appendStringInfoString(&result,
+						   "</xsd:complexType>\n\n");
+
+	appendStringInfo(&result,
+					 "<xsd:element name=\"%s\" type=\"%s\"/>\n\n",
+					 xmlcn, catalogtypename);
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL data type to an XML name; see SQL/XML:2008 section 9.4.
+ */
+static const char *
+map_sql_type_to_xml_name(Oid typeoid, int typmod)
+{
+	StringInfoData result;
+
+	initStringInfo(&result);
+
+	switch (typeoid)
+	{
+		case BPCHAROID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "CHAR");
+			else
+				appendStringInfo(&result, "CHAR_%d", typmod - VARHDRSZ);
+			break;
+		case VARCHAROID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "VARCHAR");
+			else
+				appendStringInfo(&result, "VARCHAR_%d", typmod - VARHDRSZ);
+			break;
+		case NUMERICOID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "NUMERIC");
+			else
+				appendStringInfo(&result, "NUMERIC_%d_%d",
+								 ((typmod - VARHDRSZ) >> 16) & 0xffff,
+								 (typmod - VARHDRSZ) & 0xffff);
+			break;
+		case INT4OID:
+			appendStringInfoString(&result, "INTEGER");
+			break;
+		case INT2OID:
+			appendStringInfoString(&result, "SMALLINT");
+			break;
+		case INT8OID:
+			appendStringInfoString(&result, "BIGINT");
+			break;
+		case FLOAT4OID:
+			appendStringInfoString(&result, "REAL");
+			break;
+		case FLOAT8OID:
+			appendStringInfoString(&result, "DOUBLE");
+			break;
+		case BOOLOID:
+			appendStringInfoString(&result, "BOOLEAN");
+			break;
+		case TIMEOID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "TIME");
+			else
+				appendStringInfo(&result, "TIME_%d", typmod);
+			break;
+		case TIMETZOID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "TIME_WTZ");
+			else
+				appendStringInfo(&result, "TIME_WTZ_%d", typmod);
+			break;
+		case TIMESTAMPOID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "TIMESTAMP");
+			else
+				appendStringInfo(&result, "TIMESTAMP_%d", typmod);
+			break;
+		case TIMESTAMPTZOID:
+			if (typmod == -1)
+				appendStringInfoString(&result, "TIMESTAMP_WTZ");
+			else
+				appendStringInfo(&result, "TIMESTAMP_WTZ_%d", typmod);
+			break;
+		case DATEOID:
+			appendStringInfoString(&result, "DATE");
+			break;
+		case XMLOID:
+			appendStringInfoString(&result, "XML");
+			break;
+		default:
+			{
+				HeapTuple	tuple;
+				Form_pg_type typtuple;
+
+				tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typeoid));
+				if (!HeapTupleIsValid(tuple))
+					elog(ERROR, "cache lookup failed for type %u", typeoid);
+				typtuple = (Form_pg_type) GETSTRUCT(tuple);
+
+				appendStringInfoString(&result,
+									   map_multipart_sql_identifier_to_xml_name((typtuple->typtype == TYPTYPE_DOMAIN) ? "Domain" : "UDT",
+																				get_database_name(MyDatabaseId),
+																				get_namespace_name(typtuple->typnamespace),
+																				NameStr(typtuple->typname)));
+
+				ReleaseSysCache(tuple);
+			}
+	}
+
+	return result.data;
+}
+
+
+/*
+ * Map a collection of SQL data types to XML Schema data types; see
+ * SQL/XML:2008 section 9.7.
+ */
+static const char *
+map_sql_typecoll_to_xmlschema_types(List *tupdesc_list)
+{
+	List	   *uniquetypes = NIL;
+	int			i;
+	StringInfoData result;
+	ListCell   *cell0;
+
+	/* extract all column types used in the set of TupleDescs */
+	foreach(cell0, tupdesc_list)
+	{
+		TupleDesc	tupdesc = (TupleDesc) lfirst(cell0);
+
+		for (i = 0; i < tupdesc->natts; i++)
+		{
+			Form_pg_attribute att = TupleDescAttr(tupdesc, i);
+
+			if (att->attisdropped)
+				continue;
+			uniquetypes = list_append_unique_oid(uniquetypes, att->atttypid);
+		}
+	}
+
+	/* add base types of domains */
+	foreach(cell0, uniquetypes)
+	{
+		Oid			typid = lfirst_oid(cell0);
+		Oid			basetypid = getBaseType(typid);
+
+		if (basetypid != typid)
+			uniquetypes = list_append_unique_oid(uniquetypes, basetypid);
+	}
+
+	/* Convert to textual form */
+	initStringInfo(&result);
+
+	foreach(cell0, uniquetypes)
+	{
+		appendStringInfo(&result, "%s\n",
+						 map_sql_type_to_xmlschema_type(lfirst_oid(cell0),
+														-1));
+	}
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL data type to a named XML Schema data type; see
+ * SQL/XML:2008 sections 9.5 and 9.6.
+ *
+ * (The distinction between 9.5 and 9.6 is basically that 9.6 adds
+ * a name attribute, which this function does.  The name-less version
+ * 9.5 doesn't appear to be required anywhere.)
+ */
+static const char *
+map_sql_type_to_xmlschema_type(Oid typeoid, int typmod)
+{
+	StringInfoData result;
+	const char *typename = map_sql_type_to_xml_name(typeoid, typmod);
+
+	initStringInfo(&result);
+
+	if (typeoid == XMLOID)
+	{
+		appendStringInfoString(&result,
+							   "<xsd:complexType mixed=\"true\">\n"
+							   "  <xsd:sequence>\n"
+							   "    <xsd:any name=\"element\" minOccurs=\"0\" maxOccurs=\"unbounded\" processContents=\"skip\"/>\n"
+							   "  </xsd:sequence>\n"
+							   "</xsd:complexType>\n");
+	}
+	else
+	{
+		appendStringInfo(&result,
+						 "<xsd:simpleType name=\"%s\">\n", typename);
+
+		switch (typeoid)
+		{
+			case BPCHAROID:
+			case VARCHAROID:
+			case TEXTOID:
+				appendStringInfoString(&result,
+									   "  <xsd:restriction base=\"xsd:string\">\n");
+				if (typmod != -1)
+					appendStringInfo(&result,
+									 "    <xsd:maxLength value=\"%d\"/>\n",
+									 typmod - VARHDRSZ);
+				appendStringInfoString(&result, "  </xsd:restriction>\n");
+				break;
+
+			case BYTEAOID:
+				appendStringInfo(&result,
+								 "  <xsd:restriction base=\"xsd:%s\">\n"
+								 "  </xsd:restriction>\n",
+								 xmlbinary == XMLBINARY_BASE64 ? "base64Binary" : "hexBinary");
+				break;
+
+			case NUMERICOID:
+				if (typmod != -1)
+					appendStringInfo(&result,
+									 "  <xsd:restriction base=\"xsd:decimal\">\n"
+									 "    <xsd:totalDigits value=\"%d\"/>\n"
+									 "    <xsd:fractionDigits value=\"%d\"/>\n"
+									 "  </xsd:restriction>\n",
+									 ((typmod - VARHDRSZ) >> 16) & 0xffff,
+									 (typmod - VARHDRSZ) & 0xffff);
+				break;
+
+			case INT2OID:
+				appendStringInfo(&result,
+								 "  <xsd:restriction base=\"xsd:short\">\n"
+								 "    <xsd:maxInclusive value=\"%d\"/>\n"
+								 "    <xsd:minInclusive value=\"%d\"/>\n"
+								 "  </xsd:restriction>\n",
+								 SHRT_MAX, SHRT_MIN);
+				break;
+
+			case INT4OID:
+				appendStringInfo(&result,
+								 "  <xsd:restriction base=\"xsd:int\">\n"
+								 "    <xsd:maxInclusive value=\"%d\"/>\n"
+								 "    <xsd:minInclusive value=\"%d\"/>\n"
+								 "  </xsd:restriction>\n",
+								 INT_MAX, INT_MIN);
+				break;
+
+			case INT8OID:
+				appendStringInfo(&result,
+								 "  <xsd:restriction base=\"xsd:long\">\n"
+								 "    <xsd:maxInclusive value=\"" INT64_FORMAT "\"/>\n"
+								 "    <xsd:minInclusive value=\"" INT64_FORMAT "\"/>\n"
+								 "  </xsd:restriction>\n",
+								 (((uint64) 1) << (sizeof(int64) * 8 - 1)) - 1,
+								 (((uint64) 1) << (sizeof(int64) * 8 - 1)));
+				break;
+
+			case FLOAT4OID:
+				appendStringInfoString(&result,
+									   "  <xsd:restriction base=\"xsd:float\"></xsd:restriction>\n");
+				break;
+
+			case FLOAT8OID:
+				appendStringInfoString(&result,
+									   "  <xsd:restriction base=\"xsd:double\"></xsd:restriction>\n");
+				break;
+
+			case BOOLOID:
+				appendStringInfoString(&result,
+									   "  <xsd:restriction base=\"xsd:boolean\"></xsd:restriction>\n");
+				break;
+
+			case TIMEOID:
+			case TIMETZOID:
+				{
+					const char *tz = (typeoid == TIMETZOID ? "(+|-)\\p{Nd}{2}:\\p{Nd}{2}" : "");
+
+					if (typmod == -1)
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:time\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}(.\\p{Nd}+)?%s\"/>\n"
+										 "  </xsd:restriction>\n", tz);
+					else if (typmod == 0)
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:time\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}%s\"/>\n"
+										 "  </xsd:restriction>\n", tz);
+					else
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:time\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}.\\p{Nd}{%d}%s\"/>\n"
+										 "  </xsd:restriction>\n", typmod - VARHDRSZ, tz);
+					break;
+				}
+
+			case TIMESTAMPOID:
+			case TIMESTAMPTZOID:
+				{
+					const char *tz = (typeoid == TIMESTAMPTZOID ? "(+|-)\\p{Nd}{2}:\\p{Nd}{2}" : "");
+
+					if (typmod == -1)
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:dateTime\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{4}-\\p{Nd}{2}-\\p{Nd}{2}T\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}(.\\p{Nd}+)?%s\"/>\n"
+										 "  </xsd:restriction>\n", tz);
+					else if (typmod == 0)
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:dateTime\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{4}-\\p{Nd}{2}-\\p{Nd}{2}T\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}%s\"/>\n"
+										 "  </xsd:restriction>\n", tz);
+					else
+						appendStringInfo(&result,
+										 "  <xsd:restriction base=\"xsd:dateTime\">\n"
+										 "    <xsd:pattern value=\"\\p{Nd}{4}-\\p{Nd}{2}-\\p{Nd}{2}T\\p{Nd}{2}:\\p{Nd}{2}:\\p{Nd}{2}.\\p{Nd}{%d}%s\"/>\n"
+										 "  </xsd:restriction>\n", typmod - VARHDRSZ, tz);
+					break;
+				}
+
+			case DATEOID:
+				appendStringInfoString(&result,
+									   "  <xsd:restriction base=\"xsd:date\">\n"
+									   "    <xsd:pattern value=\"\\p{Nd}{4}-\\p{Nd}{2}-\\p{Nd}{2}\"/>\n"
+									   "  </xsd:restriction>\n");
+				break;
+
+			default:
+				if (get_typtype(typeoid) == TYPTYPE_DOMAIN)
+				{
+					Oid			base_typeoid;
+					int32		base_typmod = -1;
+
+					base_typeoid = getBaseTypeAndTypmod(typeoid, &base_typmod);
+
+					appendStringInfo(&result,
+									 "  <xsd:restriction base=\"%s\"/>\n",
+									 map_sql_type_to_xml_name(base_typeoid, base_typmod));
+				}
+				break;
+		}
+		appendStringInfoString(&result, "</xsd:simpleType>\n");
+	}
+
+	return result.data;
+}
+
+
+/*
+ * Map an SQL row to an XML element, taking the row from the active
+ * SPI cursor.  See also SQL/XML:2008 section 9.10.
+ */
+static void
+SPI_sql_row_to_xmlelement(uint64 rownum, StringInfo result, char *tablename,
+						  bool nulls, bool tableforest,
+						  const char *targetns, bool top_level)
+{
+	int			i;
+	char	   *xmltn;
+
+	if (tablename)
+		xmltn = map_sql_identifier_to_xml_name(tablename, true, false);
+	else
+	{
+		if (tableforest)
+			xmltn = "row";
+		else
+			xmltn = "table";
+	}
+
+	if (tableforest)
+		xmldata_root_element_start(result, xmltn, NULL, targetns, top_level);
+	else
+		appendStringInfoString(result, "<row>\n");
+
+	for (i = 1; i <= SPI_tuptable->tupdesc->natts; i++)
+	{
+		char	   *colname;
+		Datum		colval;
+		bool		isnull;
+
+		colname = map_sql_identifier_to_xml_name(SPI_fname(SPI_tuptable->tupdesc, i),
+												 true, false);
+		colval = SPI_getbinval(SPI_tuptable->vals[rownum],
+							   SPI_tuptable->tupdesc,
+							   i,
+							   &isnull);
+		if (isnull)
+		{
+			if (nulls)
+				appendStringInfo(result, "  <%s xsi:nil=\"true\"/>\n", colname);
+		}
+		else
+			appendStringInfo(result, "  <%s>%s</%s>\n",
+							 colname,
+							 map_sql_value_to_xml_value(colval,
+														SPI_gettypeid(SPI_tuptable->tupdesc, i), true),
+							 colname);
+	}
+
+	if (tableforest)
+	{
+		xmldata_root_element_end(result, xmltn);
+		appendStringInfoChar(result, '\n');
+	}
+	else
+		appendStringInfoString(result, "</row>\n\n");
+}
+
+
+/*
+ * XPath related functions
+ */
+
+#ifdef USE_LIBXML
+
+/*
+ * Convert XML node to text.
+ *
+ * For attribute and text nodes, return the escaped text.  For anything else,
+ * dump the whole subtree.
+ */
+static text *
+xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt)
+{
+	xmltype    *result = NULL;
+
+	if (cur->type != XML_ATTRIBUTE_NODE && cur->type != XML_TEXT_NODE)
+	{
+		void		(*volatile nodefree) (xmlNodePtr) = NULL;
+		volatile xmlBufferPtr buf = NULL;
+		volatile xmlNodePtr cur_copy = NULL;
+
+		PG_TRY();
+		{
+			int			bytes;
+
+			buf = xmlBufferCreate();
+			if (buf == NULL || xmlerrcxt->err_occurred)
+				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+							"could not allocate xmlBuffer");
+
+			/*
+			 * Produce a dump of the node that we can serialize.  xmlNodeDump
+			 * does that, but the result of that function won't contain
+			 * namespace definitions from ancestor nodes, so we first do a
+			 * xmlCopyNode() which duplicates the node along with its required
+			 * namespace definitions.
+			 *
+			 * Some old libxml2 versions such as 2.7.6 produce partially
+			 * broken XML_DOCUMENT_NODE nodes (unset content field) when
+			 * copying them.  xmlNodeDump of such a node works fine, but
+			 * xmlFreeNode crashes; set us up to call xmlFreeDoc instead.
+			 */
+			cur_copy = xmlCopyNode(cur, 1);
+			if (cur_copy == NULL || xmlerrcxt->err_occurred)
+				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+							"could not copy node");
+			nodefree = (cur_copy->type == XML_DOCUMENT_NODE) ?
+				(void (*) (xmlNodePtr)) xmlFreeDoc : xmlFreeNode;
+
+			bytes = xmlNodeDump(buf, NULL, cur_copy, 0, 0);
+			if (bytes == -1 || xmlerrcxt->err_occurred)
+				xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+							"could not dump node");
+
+			result = xmlBuffer_to_xmltype(buf);
+		}
+		PG_FINALLY();
+		{
+			if (nodefree)
+				nodefree(cur_copy);
+			if (buf)
+				xmlBufferFree(buf);
+		}
+		PG_END_TRY();
+	}
+	else
+	{
+		xmlChar    *str;
+
+		str = xmlXPathCastNodeToString(cur);
+		PG_TRY();
+		{
+			/* Here we rely on XML having the same representation as TEXT */
+			char	   *escaped = escape_xml((char *) str);
+
+			result = (xmltype *) cstring_to_text(escaped);
+			pfree(escaped);
+		}
+		PG_FINALLY();
+		{
+			xmlFree(str);
+		}
+		PG_END_TRY();
+	}
+
+	return result;
+}
+
+/*
+ * Convert an XML XPath object (the result of evaluating an XPath expression)
+ * to an array of xml values, which are appended to astate.  The function
+ * result value is the number of elements in the array.
+ *
+ * If "astate" is NULL then we don't generate the array value, but we still
+ * return the number of elements it would have had.
+ *
+ * Nodesets are converted to an array containing the nodes' textual
+ * representations.  Primitive values (float, double, string) are converted
+ * to a single-element array containing the value's string representation.
+ */
+static int
+xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
+					   ArrayBuildState *astate,
+					   PgXmlErrorContext *xmlerrcxt)
+{
+	int			result = 0;
+	Datum		datum;
+	Oid			datumtype;
+	char	   *result_str;
+
+	switch (xpathobj->type)
+	{
+		case XPATH_NODESET:
+			if (xpathobj->nodesetval != NULL)
+			{
+				result = xpathobj->nodesetval->nodeNr;
+				if (astate != NULL)
+				{
+					int			i;
+
+					for (i = 0; i < result; i++)
+					{
+						datum = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i],
+																	 xmlerrcxt));
+						(void) accumArrayResult(astate, datum, false,
+												XMLOID, CurrentMemoryContext);
+					}
+				}
+			}
+			return result;
+
+		case XPATH_BOOLEAN:
+			if (astate == NULL)
+				return 1;
+			datum = BoolGetDatum(xpathobj->boolval);
+			datumtype = BOOLOID;
+			break;
+
+		case XPATH_NUMBER:
+			if (astate == NULL)
+				return 1;
+			datum = Float8GetDatum(xpathobj->floatval);
+			datumtype = FLOAT8OID;
+			break;
+
+		case XPATH_STRING:
+			if (astate == NULL)
+				return 1;
+			datum = CStringGetDatum((char *) xpathobj->stringval);
+			datumtype = CSTRINGOID;
+			break;
+
+		default:
+			elog(ERROR, "xpath expression result type %d is unsupported",
+				 xpathobj->type);
+			return 0;			/* keep compiler quiet */
+	}
+
+	/* Common code for scalar-value cases */
+	result_str = map_sql_value_to_xml_value(datum, datumtype, true);
+	datum = PointerGetDatum(cstring_to_xmltype(result_str));
+	(void) accumArrayResult(astate, datum, false,
+							XMLOID, CurrentMemoryContext);
+	return 1;
+}
+
+
+/*
+ * Common code for xpath() and xmlexists()
+ *
+ * Evaluate XPath expression and return number of nodes in res_nitems
+ * and array of XML values in astate.  Either of those pointers can be
+ * NULL if the corresponding result isn't wanted.
+ *
+ * It is up to the user to ensure that the XML passed is in fact
+ * an XML document - XPath doesn't work easily on fragments without
+ * a context node being known.
+ */
+static void
+xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
+			   int *res_nitems, ArrayBuildState *astate)
+{
+	PgXmlErrorContext *xmlerrcxt;
+	volatile xmlParserCtxtPtr ctxt = NULL;
+	volatile xmlDocPtr doc = NULL;
+	volatile xmlXPathContextPtr xpathctx = NULL;
+	volatile xmlXPathCompExprPtr xpathcomp = NULL;
+	volatile xmlXPathObjectPtr xpathobj = NULL;
+	char	   *datastr;
+	int32		len;
+	int32		xpath_len;
+	xmlChar    *string;
+	xmlChar    *xpath_expr;
+	size_t		xmldecl_len = 0;
+	int			i;
+	int			ndim;
+	Datum	   *ns_names_uris;
+	bool	   *ns_names_uris_nulls;
+	int			ns_count;
+
+	/*
+	 * Namespace mappings are passed as text[].  If an empty array is passed
+	 * (ndim = 0, "0-dimensional"), then there are no namespace mappings.
+	 * Else, a 2-dimensional array with length of the second axis being equal
+	 * to 2 should be passed, i.e., every subarray contains 2 elements, the
+	 * first element defining the name, the second one the URI.  Example:
+	 * ARRAY[ARRAY['myns', 'http://example.com'], ARRAY['myns2',
+	 * 'http://example2.com']].
+	 */
+	ndim = namespaces ? ARR_NDIM(namespaces) : 0;
+	if (ndim != 0)
+	{
+		int		   *dims;
+
+		dims = ARR_DIMS(namespaces);
+
+		if (ndim != 2 || dims[1] != 2)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_EXCEPTION),
+					 errmsg("invalid array for XML namespace mapping"),
+					 errdetail("The array must be two-dimensional with length of the second axis equal to 2.")));
+
+		Assert(ARR_ELEMTYPE(namespaces) == TEXTOID);
+
+		deconstruct_array(namespaces, TEXTOID, -1, false, TYPALIGN_INT,
+						  &ns_names_uris, &ns_names_uris_nulls,
+						  &ns_count);
+
+		Assert((ns_count % 2) == 0);	/* checked above */
+		ns_count /= 2;			/* count pairs only */
+	}
+	else
+	{
+		ns_names_uris = NULL;
+		ns_names_uris_nulls = NULL;
+		ns_count = 0;
+	}
+
+	datastr = VARDATA(data);
+	len = VARSIZE(data) - VARHDRSZ;
+	xpath_len = VARSIZE_ANY_EXHDR(xpath_expr_text);
+	if (xpath_len == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_EXCEPTION),
+				 errmsg("empty XPath expression")));
+
+	string = pg_xmlCharStrndup(datastr, len);
+	xpath_expr = pg_xmlCharStrndup(VARDATA_ANY(xpath_expr_text), xpath_len);
+
+	/*
+	 * In a UTF8 database, skip any xml declaration, which might assert
+	 * another encoding.  Ignore parse_xml_decl() failure, letting
+	 * xmlCtxtReadMemory() report parse errors.  Documentation disclaims
+	 * xpath() support for non-ASCII data in non-UTF8 databases, so leave
+	 * those scenarios bug-compatible with historical behavior.
+	 */
+	if (GetDatabaseEncoding() == PG_UTF8)
+		parse_xml_decl(string, &xmldecl_len, NULL, NULL, NULL);
+
+	xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_ALL);
+
+	PG_TRY();
+	{
+		xmlInitParser();
+
+		/*
+		 * redundant XML parsing (two parsings for the same value during one
+		 * command execution are possible)
+		 */
+		ctxt = xmlNewParserCtxt();
+		if (ctxt == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate parser context");
+		doc = xmlCtxtReadMemory(ctxt, (char *) string + xmldecl_len,
+								len - xmldecl_len, NULL, NULL, 0);
+		if (doc == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+						"could not parse XML document");
+		xpathctx = xmlXPathNewContext(doc);
+		if (xpathctx == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate XPath context");
+		xpathctx->node = (xmlNodePtr) doc;
+
+		/* register namespaces, if any */
+		if (ns_count > 0)
+		{
+			for (i = 0; i < ns_count; i++)
+			{
+				char	   *ns_name;
+				char	   *ns_uri;
+
+				if (ns_names_uris_nulls[i * 2] ||
+					ns_names_uris_nulls[i * 2 + 1])
+					ereport(ERROR,
+							(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+							 errmsg("neither namespace name nor URI may be null")));
+				ns_name = TextDatumGetCString(ns_names_uris[i * 2]);
+				ns_uri = TextDatumGetCString(ns_names_uris[i * 2 + 1]);
+				if (xmlXPathRegisterNs(xpathctx,
+									   (xmlChar *) ns_name,
+									   (xmlChar *) ns_uri) != 0)
+					ereport(ERROR,	/* is this an internal error??? */
+							(errmsg("could not register XML namespace with name \"%s\" and URI \"%s\"",
+									ns_name, ns_uri)));
+			}
+		}
+
+		xpathcomp = xmlXPathCompile(xpath_expr);
+		if (xpathcomp == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
+						"invalid XPath expression");
+
+		/*
+		 * Version 2.6.27 introduces a function named
+		 * xmlXPathCompiledEvalToBoolean, which would be enough for xmlexists,
+		 * but we can derive the existence by whether any nodes are returned,
+		 * thereby preventing a library version upgrade and keeping the code
+		 * the same.
+		 */
+		xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
+		if (xpathobj == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
+						"could not create XPath object");
+
+		/*
+		 * Extract the results as requested.
+		 */
+		if (res_nitems != NULL)
+			*res_nitems = xml_xpathobjtoxmlarray(xpathobj, astate, xmlerrcxt);
+		else
+			(void) xml_xpathobjtoxmlarray(xpathobj, astate, xmlerrcxt);
+	}
+	PG_CATCH();
+	{
+		if (xpathobj)
+			xmlXPathFreeObject(xpathobj);
+		if (xpathcomp)
+			xmlXPathFreeCompExpr(xpathcomp);
+		if (xpathctx)
+			xmlXPathFreeContext(xpathctx);
+		if (doc)
+			xmlFreeDoc(doc);
+		if (ctxt)
+			xmlFreeParserCtxt(ctxt);
+
+		pg_xml_done(xmlerrcxt, true);
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	xmlXPathFreeObject(xpathobj);
+	xmlXPathFreeCompExpr(xpathcomp);
+	xmlXPathFreeContext(xpathctx);
+	xmlFreeDoc(doc);
+	xmlFreeParserCtxt(ctxt);
+
+	pg_xml_done(xmlerrcxt, false);
+}
+#endif							/* USE_LIBXML */
+
+/*
+ * Evaluate XPath expression and return array of XML values.
+ *
+ * As we have no support of XQuery sequences yet, this function seems
+ * to be the most useful one (array of XML functions plays a role of
+ * some kind of substitution for XQuery sequences).
+ */
+Datum
+xpath(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *xpath_expr_text = PG_GETARG_TEXT_PP(0);
+	xmltype    *data = PG_GETARG_XML_P(1);
+	ArrayType  *namespaces = PG_GETARG_ARRAYTYPE_P(2);
+	ArrayBuildState *astate;
+
+	astate = initArrayResult(XMLOID, CurrentMemoryContext, true);
+	xpath_internal(xpath_expr_text, data, namespaces,
+				   NULL, astate);
+	PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+/*
+ * Determines if the node specified by the supplied XPath exists
+ * in a given XML document, returning a boolean.
+ */
+Datum
+xmlexists(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *xpath_expr_text = PG_GETARG_TEXT_PP(0);
+	xmltype    *data = PG_GETARG_XML_P(1);
+	int			res_nitems;
+
+	xpath_internal(xpath_expr_text, data, NULL,
+				   &res_nitems, NULL);
+
+	PG_RETURN_BOOL(res_nitems > 0);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+/*
+ * Determines if the node specified by the supplied XPath exists
+ * in a given XML document, returning a boolean. Differs from
+ * xmlexists as it supports namespaces and is not defined in SQL/XML.
+ */
+Datum
+xpath_exists(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *xpath_expr_text = PG_GETARG_TEXT_PP(0);
+	xmltype    *data = PG_GETARG_XML_P(1);
+	ArrayType  *namespaces = PG_GETARG_ARRAYTYPE_P(2);
+	int			res_nitems;
+
+	xpath_internal(xpath_expr_text, data, namespaces,
+				   &res_nitems, NULL);
+
+	PG_RETURN_BOOL(res_nitems > 0);
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif
+}
+
+/*
+ * Functions for checking well-formed-ness
+ */
+
+#ifdef USE_LIBXML
+static bool
+wellformed_xml(text *data, XmlOptionType xmloption_arg)
+{
+	bool		result;
+	volatile xmlDocPtr doc = NULL;
+
+	/* We want to catch any exceptions and return false */
+	PG_TRY();
+	{
+		doc = xml_parse(data, xmloption_arg, true, GetDatabaseEncoding());
+		result = true;
+	}
+	PG_CATCH();
+	{
+		FlushErrorState();
+		result = false;
+	}
+	PG_END_TRY();
+
+	if (doc)
+		xmlFreeDoc(doc);
+
+	return result;
+}
+#endif
+
+Datum
+xml_is_well_formed(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *data = PG_GETARG_TEXT_PP(0);
+
+	PG_RETURN_BOOL(wellformed_xml(data, xmloption));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif							/* not USE_LIBXML */
+}
+
+Datum
+xml_is_well_formed_document(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *data = PG_GETARG_TEXT_PP(0);
+
+	PG_RETURN_BOOL(wellformed_xml(data, XMLOPTION_DOCUMENT));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif							/* not USE_LIBXML */
+}
+
+Datum
+xml_is_well_formed_content(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+	text	   *data = PG_GETARG_TEXT_PP(0);
+
+	PG_RETURN_BOOL(wellformed_xml(data, XMLOPTION_CONTENT));
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * support functions for XMLTABLE
+ *
+ */
+#ifdef USE_LIBXML
+
+/*
+ * Returns private data from executor state. Ensure validity by check with
+ * MAGIC number.
+ */
+static inline XmlTableBuilderData *
+GetXmlTableBuilderPrivateData(TableFuncScanState *state, const char *fname)
+{
+	XmlTableBuilderData *result;
+
+	if (!IsA(state, TableFuncScanState))
+		elog(ERROR, "%s called with invalid TableFuncScanState", fname);
+	result = (XmlTableBuilderData *) state->opaque;
+	if (result->magic != XMLTABLE_CONTEXT_MAGIC)
+		elog(ERROR, "%s called with invalid TableFuncScanState", fname);
+
+	return result;
+}
+#endif
+
+/*
+ * XmlTableInitOpaque
+ *		Fill in TableFuncScanState->opaque for XmlTable processor; initialize
+ *		the XML parser.
+ *
+ * Note: Because we call pg_xml_init() here and pg_xml_done() in
+ * XmlTableDestroyOpaque, it is critical for robustness that no other
+ * executor nodes run until this node is processed to completion.  Caller
+ * must execute this to completion (probably filling a tuplestore to exhaust
+ * this node in a single pass) instead of using row-per-call mode.
+ */
+static void
+XmlTableInitOpaque(TableFuncScanState *state, int natts)
+{
+#ifdef USE_LIBXML
+	volatile xmlParserCtxtPtr ctxt = NULL;
+	XmlTableBuilderData *xtCxt;
+	PgXmlErrorContext *xmlerrcxt;
+
+	xtCxt = palloc0(sizeof(XmlTableBuilderData));
+	xtCxt->magic = XMLTABLE_CONTEXT_MAGIC;
+	xtCxt->natts = natts;
+	xtCxt->xpathscomp = palloc0(sizeof(xmlXPathCompExprPtr) * natts);
+
+	xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_ALL);
+
+	PG_TRY();
+	{
+		xmlInitParser();
+
+		ctxt = xmlNewParserCtxt();
+		if (ctxt == NULL || xmlerrcxt->err_occurred)
+			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate parser context");
+	}
+	PG_CATCH();
+	{
+		if (ctxt != NULL)
+			xmlFreeParserCtxt(ctxt);
+
+		pg_xml_done(xmlerrcxt, true);
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	xtCxt->xmlerrcxt = xmlerrcxt;
+	xtCxt->ctxt = ctxt;
+
+	state->opaque = xtCxt;
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableSetDocument
+ *		Install the input document
+ */
+static void
+XmlTableSetDocument(TableFuncScanState *state, Datum value)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+	xmltype    *xmlval = DatumGetXmlP(value);
+	char	   *str;
+	xmlChar    *xstr;
+	int			length;
+	volatile xmlDocPtr doc = NULL;
+	volatile xmlXPathContextPtr xpathcxt = NULL;
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableSetDocument");
+
+	/*
+	 * Use out function for casting to string (remove encoding property). See
+	 * comment in xml_out.
+	 */
+	str = xml_out_internal(xmlval, 0);
+
+	length = strlen(str);
+	xstr = pg_xmlCharStrndup(str, length);
+
+	PG_TRY();
+	{
+		doc = xmlCtxtReadMemory(xtCxt->ctxt, (char *) xstr, length, NULL, NULL, 0);
+		if (doc == NULL || xtCxt->xmlerrcxt->err_occurred)
+			xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+						"could not parse XML document");
+		xpathcxt = xmlXPathNewContext(doc);
+		if (xpathcxt == NULL || xtCxt->xmlerrcxt->err_occurred)
+			xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+						"could not allocate XPath context");
+		xpathcxt->node = (xmlNodePtr) doc;
+	}
+	PG_CATCH();
+	{
+		if (xpathcxt != NULL)
+			xmlXPathFreeContext(xpathcxt);
+		if (doc != NULL)
+			xmlFreeDoc(doc);
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	xtCxt->doc = doc;
+	xtCxt->xpathcxt = xpathcxt;
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableSetNamespace
+ *		Add a namespace declaration
+ */
+static void
+XmlTableSetNamespace(TableFuncScanState *state, const char *name, const char *uri)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+
+	if (name == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("DEFAULT namespace is not supported")));
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableSetNamespace");
+
+	if (xmlXPathRegisterNs(xtCxt->xpathcxt,
+						   pg_xmlCharStrndup(name, strlen(name)),
+						   pg_xmlCharStrndup(uri, strlen(uri))))
+		xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_DATA_EXCEPTION,
+					"could not set XML namespace");
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableSetRowFilter
+ *		Install the row-filter Xpath expression.
+ */
+static void
+XmlTableSetRowFilter(TableFuncScanState *state, const char *path)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+	xmlChar    *xstr;
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableSetRowFilter");
+
+	if (*path == '\0')
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_EXCEPTION),
+				 errmsg("row path filter must not be empty string")));
+
+	xstr = pg_xmlCharStrndup(path, strlen(path));
+
+	xtCxt->xpathcomp = xmlXPathCompile(xstr);
+	if (xtCxt->xpathcomp == NULL || xtCxt->xmlerrcxt->err_occurred)
+		xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_SYNTAX_ERROR,
+					"invalid XPath expression");
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableSetColumnFilter
+ *		Install the column-filter Xpath expression, for the given column.
+ */
+static void
+XmlTableSetColumnFilter(TableFuncScanState *state, const char *path, int colnum)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+	xmlChar    *xstr;
+
+	AssertArg(PointerIsValid(path));
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableSetColumnFilter");
+
+	if (*path == '\0')
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_EXCEPTION),
+				 errmsg("column path filter must not be empty string")));
+
+	xstr = pg_xmlCharStrndup(path, strlen(path));
+
+	xtCxt->xpathscomp[colnum] = xmlXPathCompile(xstr);
+	if (xtCxt->xpathscomp[colnum] == NULL || xtCxt->xmlerrcxt->err_occurred)
+		xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_DATA_EXCEPTION,
+					"invalid XPath expression");
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableFetchRow
+ *		Prepare the next "current" tuple for upcoming GetValue calls.
+ *		Returns false if the row-filter expression returned no more rows.
+ */
+static bool
+XmlTableFetchRow(TableFuncScanState *state)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableFetchRow");
+
+	/*
+	 * XmlTable returns table - set of composite values. The error context, is
+	 * used for producement more values, between two calls, there can be
+	 * created and used another libxml2 error context. It is libxml2 global
+	 * value, so it should be refreshed any time before any libxml2 usage,
+	 * that is finished by returning some value.
+	 */
+	xmlSetStructuredErrorFunc((void *) xtCxt->xmlerrcxt, xml_errorHandler);
+
+	if (xtCxt->xpathobj == NULL)
+	{
+		xtCxt->xpathobj = xmlXPathCompiledEval(xtCxt->xpathcomp, xtCxt->xpathcxt);
+		if (xtCxt->xpathobj == NULL || xtCxt->xmlerrcxt->err_occurred)
+			xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
+						"could not create XPath object");
+
+		xtCxt->row_count = 0;
+	}
+
+	if (xtCxt->xpathobj->type == XPATH_NODESET)
+	{
+		if (xtCxt->xpathobj->nodesetval != NULL)
+		{
+			if (xtCxt->row_count++ < xtCxt->xpathobj->nodesetval->nodeNr)
+				return true;
+		}
+	}
+
+	return false;
+#else
+	NO_XML_SUPPORT();
+	return false;
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableGetValue
+ *		Return the value for column number 'colnum' for the current row.  If
+ *		column -1 is requested, return representation of the whole row.
+ *
+ * This leaks memory, so be sure to reset often the context in which it's
+ * called.
+ */
+static Datum
+XmlTableGetValue(TableFuncScanState *state, int colnum,
+				 Oid typid, int32 typmod, bool *isnull)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+	Datum		result = (Datum) 0;
+	xmlNodePtr	cur;
+	char	   *cstr = NULL;
+	volatile xmlXPathObjectPtr xpathobj = NULL;
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableGetValue");
+
+	Assert(xtCxt->xpathobj &&
+		   xtCxt->xpathobj->type == XPATH_NODESET &&
+		   xtCxt->xpathobj->nodesetval != NULL);
+
+	/* Propagate context related error context to libxml2 */
+	xmlSetStructuredErrorFunc((void *) xtCxt->xmlerrcxt, xml_errorHandler);
+
+	*isnull = false;
+
+	cur = xtCxt->xpathobj->nodesetval->nodeTab[xtCxt->row_count - 1];
+
+	Assert(xtCxt->xpathscomp[colnum] != NULL);
+
+	PG_TRY();
+	{
+		/* Set current node as entry point for XPath evaluation */
+		xtCxt->xpathcxt->node = cur;
+
+		/* Evaluate column path */
+		xpathobj = xmlXPathCompiledEval(xtCxt->xpathscomp[colnum], xtCxt->xpathcxt);
+		if (xpathobj == NULL || xtCxt->xmlerrcxt->err_occurred)
+			xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
+						"could not create XPath object");
+
+		/*
+		 * There are four possible cases, depending on the number of nodes
+		 * returned by the XPath expression and the type of the target column:
+		 * a) XPath returns no nodes.  b) The target type is XML (return all
+		 * as XML).  For non-XML return types:  c) One node (return content).
+		 * d) Multiple nodes (error).
+		 */
+		if (xpathobj->type == XPATH_NODESET)
+		{
+			int			count = 0;
+
+			if (xpathobj->nodesetval != NULL)
+				count = xpathobj->nodesetval->nodeNr;
+
+			if (xpathobj->nodesetval == NULL || count == 0)
+			{
+				*isnull = true;
+			}
+			else
+			{
+				if (typid == XMLOID)
+				{
+					text	   *textstr;
+					StringInfoData str;
+
+					/* Concatenate serialized values */
+					initStringInfo(&str);
+					for (int i = 0; i < count; i++)
+					{
+						textstr =
+							xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i],
+												 xtCxt->xmlerrcxt);
+
+						appendStringInfoText(&str, textstr);
+					}
+					cstr = str.data;
+				}
+				else
+				{
+					xmlChar    *str;
+
+					if (count > 1)
+						ereport(ERROR,
+								(errcode(ERRCODE_CARDINALITY_VIOLATION),
+								 errmsg("more than one value returned by column XPath expression")));
+
+					str = xmlXPathCastNodeSetToString(xpathobj->nodesetval);
+					cstr = str ? xml_pstrdup_and_free(str) : "";
+				}
+			}
+		}
+		else if (xpathobj->type == XPATH_STRING)
+		{
+			/* Content should be escaped when target will be XML */
+			if (typid == XMLOID)
+				cstr = escape_xml((char *) xpathobj->stringval);
+			else
+				cstr = (char *) xpathobj->stringval;
+		}
+		else if (xpathobj->type == XPATH_BOOLEAN)
+		{
+			char		typcategory;
+			bool		typispreferred;
+			xmlChar    *str;
+
+			/* Allow implicit casting from boolean to numbers */
+			get_type_category_preferred(typid, &typcategory, &typispreferred);
+
+			if (typcategory != TYPCATEGORY_NUMERIC)
+				str = xmlXPathCastBooleanToString(xpathobj->boolval);
+			else
+				str = xmlXPathCastNumberToString(xmlXPathCastBooleanToNumber(xpathobj->boolval));
+
+			cstr = xml_pstrdup_and_free(str);
+		}
+		else if (xpathobj->type == XPATH_NUMBER)
+		{
+			xmlChar    *str;
+
+			str = xmlXPathCastNumberToString(xpathobj->floatval);
+			cstr = xml_pstrdup_and_free(str);
+		}
+		else
+			elog(ERROR, "unexpected XPath object type %u", xpathobj->type);
+
+		/*
+		 * By here, either cstr contains the result value, or the isnull flag
+		 * has been set.
+		 */
+		Assert(cstr || *isnull);
+
+		if (!*isnull)
+			result = InputFunctionCall(&state->in_functions[colnum],
+									   cstr,
+									   state->typioparams[colnum],
+									   typmod);
+	}
+	PG_FINALLY();
+	{
+		if (xpathobj != NULL)
+			xmlXPathFreeObject(xpathobj);
+	}
+	PG_END_TRY();
+
+	return result;
+#else
+	NO_XML_SUPPORT();
+	return 0;
+#endif							/* not USE_LIBXML */
+}
+
+/*
+ * XmlTableDestroyOpaque
+ *		Release all libxml2 resources
+ */
+static void
+XmlTableDestroyOpaque(TableFuncScanState *state)
+{
+#ifdef USE_LIBXML
+	XmlTableBuilderData *xtCxt;
+
+	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableDestroyOpaque");
+
+	/* Propagate context related error context to libxml2 */
+	xmlSetStructuredErrorFunc((void *) xtCxt->xmlerrcxt, xml_errorHandler);
+
+	if (xtCxt->xpathscomp != NULL)
+	{
+		int			i;
+
+		for (i = 0; i < xtCxt->natts; i++)
+			if (xtCxt->xpathscomp[i] != NULL)
+				xmlXPathFreeCompExpr(xtCxt->xpathscomp[i]);
+	}
+
+	if (xtCxt->xpathobj != NULL)
+		xmlXPathFreeObject(xtCxt->xpathobj);
+	if (xtCxt->xpathcomp != NULL)
+		xmlXPathFreeCompExpr(xtCxt->xpathcomp);
+	if (xtCxt->xpathcxt != NULL)
+		xmlXPathFreeContext(xtCxt->xpathcxt);
+	if (xtCxt->doc != NULL)
+		xmlFreeDoc(xtCxt->doc);
+	if (xtCxt->ctxt != NULL)
+		xmlFreeParserCtxt(xtCxt->ctxt);
+
+	pg_xml_done(xtCxt->xmlerrcxt, true);
+
+	/* not valid anymore */
+	xtCxt->magic = 0;
+	state->opaque = NULL;
+
+#else
+	NO_XML_SUPPORT();
+#endif							/* not USE_LIBXML */
+}