Hi
On 23.01.25 07:50, Pavel Stehule wrote:
> I think so in this form (just forward input to output) I have no
> objection.
>
> There is a benefit with a) possible zero work with migration from db2,
> b) nobody needs to repeat a work which is a correct implementation of
> XMLDOCUMENT function.
>
> Maybe opened question can be implementation like classic scalar
> function or via XmlExpr
>
> In this moment I prefer to use XmlExpr from consistency reasons
To keep it consistent with the existing code, I think this function is
in the right place. There are similar functions in xml.c, e.g.
xmltotext, texttoxml.
I updated the function comment and commit message (v4 attached) to make
things clearer.
Since the status of this patch is waiting on author, is there anything
else I should take a look / improve?
Thanks!
Best regards,Jim
From a4050417a9a6b46fb8429acf8c4a999f457ec85f Mon Sep 17 00:00:00 2001
From: Jim Jones <jim.jo...@uni-muenster.de>
Date: Thu, 23 Jan 2025 15:38:07 +0100
Subject: [PATCH v4] 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. Since our XML data type
corresponds to XML(CONTENT(ANY)), any expression already validated
by the input function is considered valid output for XMLDocument.
As a result, this function simply returns its input value. While
this implementation is quite trivial, it follows the SQL/XML
standard and facilitates the migration of SQL statements from
other database systems that also support X030.
Usage:
WITH t(x) AS (
VALUES
(xmlparse(DOCUMENT '<root><foo>bar</foo></root>')),
(xmlforest(42 AS foo, 73 AS bar)),
(NULL)
)
SELECT xmldocument(x) FROM t;
xmldocument
-----------------------------
<root><foo>bar</foo></root>
<foo>42</foo><bar>73</bar>
(3 rows)
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 | 19 +++++++++
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, 241 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5678e7621a..89aee841dd 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -14430,6 +14430,42 @@ 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..6fe3ed8666 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -523,6 +523,25 @@ xmlcomment(PG_FUNCTION_ARGS)
}
+/*
+ * xmldocument implements the SQL/XML function XMLDocument (X030).
+ * Since our XML data type corresponds to XML(CONTENT(ANY)), any
+ * expression already validated by the input function is considered
+ * valid output for XMLDocument. As a result, this function simply
+ * returns its input value.
+ */
+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
