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 <[email protected]>
Reviewed-by: Vik Fearing <[email protected]>
Discussion: https://postgr.es/m/[email protected]

4 files changed, 102 insertions, 0 deletions

diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index 398345ca67f..13e4296bf8f 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -1785,3 +1785,39 @@ SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH
  <foo/> | &lt;foo/&gt;
 (1 row)
 
+SELECT xmltext(NULL);
+ xmltext 
+---------
+ 
+(1 row)
+
+SELECT xmltext('');
+ xmltext 
+---------
+ 
+(1 row)
+
+SELECT xmltext('  ');
+ xmltext 
+---------
+   
+(1 row)
+
+SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
+         xmltext          
+--------------------------
+ foo `$_-+?=*^%!|/\()[]{}
+(1 row)
+
+SELECT xmltext('foo & <"bar">');
+              xmltext              
+-----------------------------------
+ foo &amp; &lt;&quot;bar&quot;&gt;
+(1 row)
+
+SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
+             xmltext             
+---------------------------------
+ x&lt;P&gt;73&lt;/P&gt;0.42truej
+(1 row)
+
diff --git a/src/test/regress/expected/xml_1.out b/src/test/regress/expected/xml_1.out
index 63b779470ff..eb9c6f2ed41 100644
--- a/src/test/regress/expected/xml_1.out
+++ b/src/test/regress/expected/xml_1.out
@@ -1402,3 +1402,26 @@ DETAIL:  This functionality requires the server to be built with libxml support.
 SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH '"<foo/>"', b xml PATH '"<foo/>"');
 ERROR:  unsupported XML feature
 DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xmltext(NULL);
+ xmltext 
+---------
+ 
+(1 row)
+
+SELECT xmltext('');
+ERROR:  unsupported XML feature
+DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xmltext('  ');
+ERROR:  unsupported XML feature
+DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
+ERROR:  unsupported XML feature
+DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xmltext('foo & <"bar">');
+ERROR:  unsupported XML feature
+DETAIL:  This functionality requires the server to be built with libxml support.
+SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
+ERROR:  unsupported XML feature
+LINE 1: SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j':...
+                             ^
+DETAIL:  This functionality requires the server to be built with libxml support.
diff --git a/src/test/regress/expected/xml_2.out b/src/test/regress/expected/xml_2.out
index 43c2558352a..c8ed8e0cfa6 100644
--- a/src/test/regress/expected/xml_2.out
+++ b/src/test/regress/expected/xml_2.out
@@ -1765,3 +1765,39 @@ SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH
  <foo/> | &lt;foo/&gt;
 (1 row)
 
+SELECT xmltext(NULL);
+ xmltext 
+---------
+ 
+(1 row)
+
+SELECT xmltext('');
+ xmltext 
+---------
+ 
+(1 row)
+
+SELECT xmltext('  ');
+ xmltext 
+---------
+   
+(1 row)
+
+SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
+         xmltext          
+--------------------------
+ foo `$_-+?=*^%!|/\()[]{}
+(1 row)
+
+SELECT xmltext('foo & <"bar">');
+              xmltext              
+-----------------------------------
+ foo &amp; &lt;&quot;bar&quot;&gt;
+(1 row)
+
+SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
+             xmltext             
+---------------------------------
+ x&lt;P&gt;73&lt;/P&gt;0.42truej
+(1 row)
+
diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index a591eea2e5d..bd4a4e7acdf 100644
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -660,3 +660,10 @@ SELECT * FROM XMLTABLE('*' PASSING '<e>pre<!--c1--><?pi arg?><![CDATA[&ent1]]><n
 \x
 
 SELECT * FROM XMLTABLE('.' PASSING XMLELEMENT(NAME a) columns a varchar(20) PATH '"<foo/>"', b xml PATH '"<foo/>"');
+
+SELECT xmltext(NULL);
+SELECT xmltext('');
+SELECT xmltext('  ');
+SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
+SELECT xmltext('foo & <"bar">');
+SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
\ No newline at end of file