On 20.01.25 23:21, Chapman Flack wrote:
> Therefore I'm thinking that, given the specifics of our XML support,
> a fully conformant and efficient XMLDOCUMENT could be implemented
> just by returning its XML argument.
After your explanation, I tend to agree.
v3, attached, incorporates these changes and updates the regression
tests accordingly.
>
> That opens a question of whether it's worth the effort to supply
> it at all. Maybe it could reduce the surprise for people coming from
> another DBMS and finding it missing, and/or be a placeholder in case
> we ever implement enough more of the newer SQL/XML standard for it
> to have a real effect.
Although quite trivial, I believe this function could still be valuable
in facilitating the migration of scripts from other database systems --
improving SQL/XML conformance also isn't a bad thing :).
Thank you again for your help in interpreting the SQL/XML standard. Much
appreciated!
Best regards, Jim
From 200cb507fb694179fd3f452a5e81017d76fa7bb1 Mon Sep 17 00:00:00 2001
From: Jim Jones <jim.jo...@uni-muenster.de>
Date: Tue, 21 Jan 2025 11:45:34 +0100
Subject: [PATCH v3] Add XMLDocument function (SQL/XML X030)
This patch adds the SQL/XML X030 function XMLDocument. It returns
an XML document from a given XML expression. An XML document node
can have any number of children nodes.
This patch also adds documentation and tests.
---
doc/src/sgml/func.sgml | 36 +++++++++++++++++
src/backend/catalog/sql_features.txt | 2 +-
src/backend/utils/adt/xml.c | 18 +++++++++
src/include/catalog/pg_proc.dat | 3 ++
src/test/regress/expected/xml.out | 58 ++++++++++++++++++++++++++++
src/test/regress/expected/xml_1.out | 47 ++++++++++++++++++++++
src/test/regress/expected/xml_2.out | 58 ++++++++++++++++++++++++++++
src/test/regress/sql/xml.sql | 19 +++++++++
8 files changed, 240 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 47370e581a..067419f0a2 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -14417,6 +14417,42 @@ SELECT xmlcomment('hello');
</para>
</sect3>
+ <sect3 id="functions-producing-xml-xmldocument">
+ <title><literal>xmldocument</literal></title>
+
+ <indexterm>
+ <primary>xmldocument</primary>
+ </indexterm>
+
+<synopsis>
+<function>xmldocument</function> ( <type>xml</type> ) <returnvalue>xml</returnvalue>
+</synopsis>
+
+ <para>
+ The <function>xmldocument</function> returns a document node from the given <type>xml</type> expression.
+ If the XML expression is NULL, the result will also be NULL.
+ </para>
+
+ <para>
+ Example:
+<screen><![CDATA[
+SELECT
+ xmldocument(
+ xmlelement(NAME foo,
+ xmlattributes(42 AS att),
+ xmlelement(NAME bar,
+ xmlconcat('va', 'lue'))
+ )
+ );
+
+ xmldocument
+--------------------------------------
+ <foo att="42"><bar>value</bar></foo>
+(1 row)
+]]></screen>
+ </para>
+ </sect3>
+
<sect3 id="functions-producing-xml-xmlconcat">
<title><literal>xmlconcat</literal></title>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..f621b6af1d 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -625,7 +625,7 @@ X015 Fields of XML type NO
X016 Persistent XML values YES
X020 XMLConcat YES
X025 XMLCast NO
-X030 XMLDocument NO
+X030 XMLDocument YES
X031 XMLElement YES
X032 XMLForest YES
X034 XMLAgg YES
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index db8d0d6a7e..b1c1f266d4 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -522,6 +522,24 @@ xmlcomment(PG_FUNCTION_ARGS)
#endif
}
+/*
+ * This implements the SQL/XML function XMLDocument (X030). As we do not
+ * have an XML(SEQUENCE) equivalent, this function simply returns any xml
+ * expression already validated by the input function. Its primary purpose
+ * is to enhance SQL/XML conformance and simplify script migrations from
+ * other database systems.
+ */
+Datum
+xmldocument(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+ xmltype *data = PG_GETARG_XML_P(0);
+ PG_RETURN_XML_P(data);
+#else
+ NO_XML_SUPPORT();
+ return 0;
+#endif /* not USE_LIBXML */
+}
Datum
xmltext(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 18560755d2..a23ea1ebc9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9017,6 +9017,9 @@
{ oid => '3813', descr => 'generate XML text node',
proname => 'xmltext', prorettype => 'xml', proargtypes => 'text',
prosrc => 'xmltext' },
+{ oid => '3814', descr => 'generate XML document',
+ proname => 'xmldocument', prorettype => 'xml', proargtypes => 'xml',
+ prosrc => 'xmldocument'},
{ oid => '2923', descr => 'map table contents to XML',
proname => 'table_to_xml', procost => '100', provolatile => 's',
diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index 2e9616acda..dcacfb6f4e 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -1873,3 +1873,61 @@ SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
x<P>73</P>0.42truej
(1 row)
+SELECT
+ xmldocument(
+ xmlelement(NAME root,
+ xmlattributes(42 AS att),
+ xmlcomment('comment'),
+ xmlelement(NAME foo,'<foo&bar>'),
+ xmlelement(NAME bar, xmlconcat('va', 'lue')),
+ xmlpi(name pi),
+ xmlelement(NAME txt, xmltext('<"&>'))
+ )
+ );
+ xmldocument
+------------------------------------------------------------------------------------------------------------------------
+ <root att="42"><!--comment--><foo><foo&bar></foo><bar>value</bar><?pi?><txt><"&></txt></root>
+(1 row)
+
+SELECT xmldocument(NULL);
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument('<foo>bar</foo>'::xml);
+ xmldocument
+----------------
+ <foo>bar</foo>
+(1 row)
+
+SELECT xmldocument('foo'::xml);
+ xmldocument
+-------------
+ foo
+(1 row)
+
+SELECT xmldocument('foo');
+ xmldocument
+-------------
+ foo
+(1 row)
+
+SELECT xmldocument('');
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument(' ');
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument(xmlcomment('comment'));
+ xmldocument
+----------------
+ <!--comment-->
+(1 row)
+
diff --git a/src/test/regress/expected/xml_1.out b/src/test/regress/expected/xml_1.out
index 7505a14077..8268ee20e5 100644
--- a/src/test/regress/expected/xml_1.out
+++ b/src/test/regress/expected/xml_1.out
@@ -1482,3 +1482,50 @@ 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.
+SELECT
+ xmldocument(
+ xmlelement(NAME root,
+ xmlattributes(42 AS att),
+ xmlcomment('comment'),
+ xmlelement(NAME foo,'<foo&bar>'),
+ xmlelement(NAME bar, xmlconcat('va', 'lue')),
+ xmlpi(name pi),
+ xmlelement(NAME txt, xmltext('<"&>'))
+ )
+ );
+ERROR: unsupported XML feature
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument(NULL);
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument('<foo>bar</foo>'::xml);
+ERROR: unsupported XML feature
+LINE 1: SELECT xmldocument('<foo>bar</foo>'::xml);
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument('foo'::xml);
+ERROR: unsupported XML feature
+LINE 1: SELECT xmldocument('foo'::xml);
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument('foo');
+ERROR: unsupported XML feature
+LINE 1: SELECT xmldocument('foo');
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument('');
+ERROR: unsupported XML feature
+LINE 1: SELECT xmldocument('');
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument(' ');
+ERROR: unsupported XML feature
+LINE 1: SELECT xmldocument(' ');
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+SELECT xmldocument(xmlcomment('comment'));
+ERROR: unsupported XML feature
+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 c07ed2b269..ce7f8302b2 100644
--- a/src/test/regress/expected/xml_2.out
+++ b/src/test/regress/expected/xml_2.out
@@ -1859,3 +1859,61 @@ SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
x<P>73</P>0.42truej
(1 row)
+SELECT
+ xmldocument(
+ xmlelement(NAME root,
+ xmlattributes(42 AS att),
+ xmlcomment('comment'),
+ xmlelement(NAME foo,'<foo&bar>'),
+ xmlelement(NAME bar, xmlconcat('va', 'lue')),
+ xmlpi(name pi),
+ xmlelement(NAME txt, xmltext('<"&>'))
+ )
+ );
+ xmldocument
+------------------------------------------------------------------------------------------------------------------------
+ <root att="42"><!--comment--><foo><foo&bar></foo><bar>value</bar><?pi?><txt><"&></txt></root>
+(1 row)
+
+SELECT xmldocument(NULL);
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument('<foo>bar</foo>'::xml);
+ xmldocument
+----------------
+ <foo>bar</foo>
+(1 row)
+
+SELECT xmldocument('foo'::xml);
+ xmldocument
+-------------
+ foo
+(1 row)
+
+SELECT xmldocument('foo');
+ xmldocument
+-------------
+ foo
+(1 row)
+
+SELECT xmldocument('');
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument(' ');
+ xmldocument
+-------------
+
+(1 row)
+
+SELECT xmldocument(xmlcomment('comment'));
+ xmldocument
+----------------
+ <!--comment-->
+(1 row)
+
diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index bac0388ac1..0089c6eaa2 100644
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -675,3 +675,22 @@ SELECT xmltext(' ');
SELECT xmltext('foo `$_-+?=*^%!|/\()[]{}');
SELECT xmltext('foo & <"bar">');
SELECT xmltext('x'|| '<P>73</P>'::xml || .42 || true || 'j'::char);
+
+SELECT
+ xmldocument(
+ xmlelement(NAME root,
+ xmlattributes(42 AS att),
+ xmlcomment('comment'),
+ xmlelement(NAME foo,'<foo&bar>'),
+ xmlelement(NAME bar, xmlconcat('va', 'lue')),
+ xmlpi(name pi),
+ xmlelement(NAME txt, xmltext('<"&>'))
+ )
+ );
+SELECT xmldocument(NULL);
+SELECT xmldocument('<foo>bar</foo>'::xml);
+SELECT xmldocument('foo'::xml);
+SELECT xmldocument('foo');
+SELECT xmldocument('');
+SELECT xmldocument(' ');
+SELECT xmldocument(xmlcomment('comment'));
--
2.34.1
