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Add XMLText function (SQL/XML X038)
This function implements the standard XMLTest function, which converts text into xml text nodes. It uses the libxml2 function xmlEncodeSpecialChars to escape predefined entities (&"<>), so that those do not cause any conflict when concatenating the text node output with existing xml documents. This also adds a note in features.sgml about not supporting XML(SEQUENCE). The SQL specification defines a RETURNING clause to a set of XML functions, where RETURNING CONTENT or RETURNING SEQUENCE can be defined. Since PostgreSQL doesn't support XML(SEQUENCE) all of these functions operate with an implicit RETURNING CONTENT. Author: Jim Jones <jim.jones@uni-muenster.de> Reviewed-by: Vik Fearing <vik@postgresfriends.org> Discussion: https://postgr.es/m/86617a66-ec95-581f-8d54-08059cca8885@uni-muenster.de
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‎doc/src/sgml/features.sgml

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@@ -199,6 +199,15 @@
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standard.
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</para>
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</listitem>
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<listitem>
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<para>
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<productname>PostgreSQL</productname> does not support the
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<literal>RETURNING CONTENT</literal> or <literal>RETURNING SEQUENCE</literal>
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clauses, functions which are defined to have these in the specification
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are implicitly returning content.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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‎doc/src/sgml/func.sgml

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@@ -14180,6 +14180,36 @@ CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple
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documents for processing in client applications.
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</para>
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<sect3 id="functions-producing-xml-xmltext">
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<title><literal>xmltext</literal></title>
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<indexterm>
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<primary>xmltext</primary>
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</indexterm>
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<synopsis>
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<function>xmltext</function> ( <type>text</type> ) <returnvalue>xml</returnvalue>
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</synopsis>
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<para>
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The function <function>xmltext</function> returns an XML value with a single
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text node containing the input argument as its content. Predefined entities
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like ampersand (<literal><![CDATA[&]]></literal>), left and right angle brackets
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(<literal><![CDATA[< >]]></literal>), and quotation marks (<literal><![CDATA[""]]></literal>)
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are escaped.
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</para>
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<para>
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Example:
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<screen><![CDATA[
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SELECT xmltext('< foo & bar >');
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xmltext
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-------------------------
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&lt; foo &amp; bar &gt;
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]]></screen>
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</para>
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</sect3>
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<sect3 id="functions-producing-xml-xmlcomment">
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<title><literal>xmlcomment</literal></title>
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‎src/backend/catalog/sql_features.txt

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@@ -633,7 +633,7 @@ X034 XMLAgg YES
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X035 XMLAgg: ORDER BY option YES
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X036 XMLComment YES
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X037 XMLPI YES
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X038 XMLText NO
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X038 XMLText YES supported except for RETURNING
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X040 Basic table mapping YES
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X041 Basic table mapping: null absent YES
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X042 Basic table mapping: null as nil YES

‎src/backend/utils/adt/xml.c

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@@ -47,6 +47,7 @@
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#ifdef USE_LIBXML
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#include <libxml/chvalid.h>
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#include <libxml/entities.h>
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#include <libxml/parser.h>
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#include <libxml/parserInternals.h>
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#include <libxml/tree.h>
@@ -513,6 +514,27 @@ xmlcomment(PG_FUNCTION_ARGS)
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}
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Datum
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xmltext(PG_FUNCTION_ARGS)
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{
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#ifdef USE_LIBXML
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text *arg = PG_GETARG_TEXT_PP(0);
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text *result;
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xmlChar *xmlbuf = NULL;
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xmlbuf = xmlEncodeSpecialChars(NULL, xml_text2xmlChar(arg));
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Assert(xmlbuf);
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result = cstring_to_text_with_len((const char *) xmlbuf, xmlStrlen(xmlbuf));
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xmlFree(xmlbuf);
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PG_RETURN_XML_P(result);
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#else
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NO_XML_SUPPORT();
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return 0;
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#endif /* not USE_LIBXML */
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}
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/*
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* TODO: xmlconcat needs to merge the notations and unparsed entities

‎src/include/catalog/pg_proc.dat

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@@ -8793,6 +8793,9 @@
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{ oid => '2922', descr => 'serialize an XML value to a character string',
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proname => 'text', prorettype => 'text', proargtypes => 'xml',
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prosrc => 'xmltotext' },
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{ oid => '3813', descr => 'generate XML text node',
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proname => 'xmltext', proisstrict => 't', prorettype => 'xml',
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proargtypes => 'text', prosrc => 'xmltext' },
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{ oid => '2923', descr => 'map table contents to XML',
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proname => 'table_to_xml', procost => '100', provolatile => 's',

‎src/test/regress/expected/xml.out

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@@ -1785,3 +1785,39 @@ SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH
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<foo/> | &lt;foo/&gt;
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(1 row)
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SELECT xmltext(NULL);
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xmltext
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---------
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(1 row)
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SELECT xmltext('');
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xmltext
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---------
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(1 row)
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SELECT xmltext(' ');
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xmltext
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---------
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(1 row)
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SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
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xmltext
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--------------------------
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foo `$_-+?=*^%!|/\()[]{}
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(1 row)
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SELECT xmltext('foo & <"bar">');
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xmltext
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-----------------------------------
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foo &amp; &lt;&quot;bar&quot;&gt;
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(1 row)
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SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
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xmltext
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---------------------------------
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x&lt;P&gt;73&lt;/P&gt;0.42truej
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(1 row)
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‎src/test/regress/expected/xml_1.out

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@@ -1402,3 +1402,26 @@ DETAIL: This functionality requires the server to be built with libxml support.
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SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH '"<foo/>"', b xml PATH '"<foo/>"');
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ERROR: unsupported XML feature
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DETAIL: This functionality requires the server to be built with libxml support.
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SELECT xmltext(NULL);
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xmltext
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---------
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(1 row)
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SELECT xmltext('');
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ERROR: unsupported XML feature
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DETAIL: This functionality requires the server to be built with libxml support.
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SELECT xmltext(' ');
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ERROR: unsupported XML feature
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DETAIL: This functionality requires the server to be built with libxml support.
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SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
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ERROR: unsupported XML feature
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DETAIL: This functionality requires the server to be built with libxml support.
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SELECT xmltext('foo & <"bar">');
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ERROR: unsupported XML feature
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DETAIL: This functionality requires the server to be built with libxml support.
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SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
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ERROR: unsupported XML feature
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LINE 1: SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j':...
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^
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DETAIL: This functionality requires the server to be built with libxml support.

‎src/test/regress/expected/xml_2.out

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@@ -1765,3 +1765,39 @@ SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH
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<foo/> | &lt;foo/&gt;
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(1 row)
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SELECT xmltext(NULL);
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xmltext
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---------
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(1 row)
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SELECT xmltext('');
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xmltext
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---------
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(1 row)
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SELECT xmltext(' ');
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xmltext
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---------
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(1 row)
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SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
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xmltext
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--------------------------
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foo `$_-+?=*^%!|/\()[]{}
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(1 row)
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SELECT xmltext('foo & <"bar">');
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xmltext
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-----------------------------------
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foo &amp; &lt;&quot;bar&quot;&gt;
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(1 row)
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SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
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xmltext
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---------------------------------
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x&lt;P&gt;73&lt;/P&gt;0.42truej
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(1 row)
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‎src/test/regress/sql/xml.sql

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@@ -660,3 +660,10 @@ SELECT * FROM XMLTABLE('*' PASSING '<e>pre<!--c1--><?pi arg?><![CDATA[&ent1]]><n
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\x
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SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH '"<foo/>"', b xml PATH '"<foo/>"');
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SELECT xmltext(NULL);
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SELECT xmltext('');
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SELECT xmltext(' ');
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SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
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SELECT xmltext('foo & <"bar">');
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SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);

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