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Add an xpath_exists() function. This is equivalent to XMLEXISTS except that
it offers support for namespace mapping. Mike Fowler, reviewed by David Fetter
This commit is contained in:
Tom Lane
@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.524 2010/08/05 18:21:17 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.525 2010/08/08 19:15:27 tgl Exp $ -->
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<chapter id="functions">
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<title>Functions and Operators</title>
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@ -8175,7 +8175,7 @@ CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple
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linkend="datatype-xml"> for information about the <type>xml</type>
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type. The function-like expressions <function>xmlparse</function>
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and <function>xmlserialize</function> for converting to and from
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type <type>xml</type> are not repeated here. Use of many of these
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type <type>xml</type> are not repeated here. Use of most of these
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functions requires the installation to have been built
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with <command>configure --with-libxml</>.
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</para>
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@ -8231,7 +8231,7 @@ SELECT xmlcomment('hello');
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<synopsis>
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<function>xmlconcat</function>(<replaceable>xml</replaceable><optional>, ...</optional>)
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</synopsis>
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<para>
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The function <function>xmlconcat</function> concatenates a list
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of individual XML values to create a single value containing an
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@ -8277,18 +8277,18 @@ SELECT xmlconcat('<?xml version="1.1"?><foo/>', '<?xml version="1.1" standalone=
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]]></screen>
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</para>
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</sect3>
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<sect3>
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<title><literal>xmlelement</literal></title>
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<indexterm>
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<primary>xmlelement</primary>
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</indexterm>
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<synopsis>
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<function>xmlelement</function>(name <replaceable>name</replaceable> <optional>, xmlattributes(<replaceable>value</replaceable> <optional>AS <replaceable>attname</replaceable></optional> <optional>, ... </optional>)</optional> <optional><replaceable>, content, ...</replaceable></optional>)
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</synopsis>
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<para>
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The <function>xmlelement</function> expression produces an XML
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element with the given name, attributes, and content.
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@ -8375,18 +8375,18 @@ SELECT xmlelement(name foo, xmlattributes('xyz' as bar),
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at which point a more precise description will appear.
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</para>
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</sect3>
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<sect3>
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<title><literal>xmlforest</literal></title>
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<indexterm>
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<primary>xmlforest</primary>
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</indexterm>
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<synopsis>
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<function>xmlforest</function>(<replaceable>content</replaceable> <optional>AS <replaceable>name</replaceable></optional> <optional>, ...</optional>)
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</synopsis>
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<para>
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The <function>xmlforest</function> expression produces an XML
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forest (sequence) of elements using the given names and content.
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@ -8432,18 +8432,18 @@ WHERE table_schema = 'pg_catalog';
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<function>xmlelement</function>.
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</para>
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</sect3>
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<sect3>
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<title><literal>xmlpi</literal></title>
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<indexterm>
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<primary>xmlpi</primary>
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</indexterm>
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<synopsis>
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<function>xmlpi</function>(name <replaceable>target</replaceable> <optional>, <replaceable>content</replaceable></optional>)
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</synopsis>
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<para>
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The <function>xmlpi</function> expression creates an XML
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processing instruction. The content, if present, must not
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@ -8461,18 +8461,18 @@ SELECT xmlpi(name php, 'echo "hello world";');
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]]></screen>
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</para>
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</sect3>
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<sect3>
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<title><literal>xmlroot</literal></title>
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<indexterm>
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<primary>xmlroot</primary>
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</indexterm>
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<synopsis>
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<function>xmlroot</function>(<replaceable>xml</replaceable>, version <replaceable>text</replaceable> | no value <optional>, standalone yes|no|no value</optional>)
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</synopsis>
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<para>
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The <function>xmlroot</function> expression alters the properties
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of the root node of an XML value. If a version is specified,
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@ -8483,7 +8483,7 @@ SELECT xmlpi(name php, 'echo "hello world";');
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<para>
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<screen><![CDATA[
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SELECT xmlroot(xmlparse(document '<?xml version="1.1"?><content>abc</content>'),
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SELECT xmlroot(xmlparse(document '<?xml version="1.1"?><content>abc</content>'),
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version '1.0', standalone yes);
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xmlroot
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@ -8636,17 +8636,19 @@ SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Tor
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<para>
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To process values of data type <type>xml</type>, PostgreSQL offers
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the function <function>xpath</function>, which evaluates XPath 1.0
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the functions <function>xpath</function> and
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<function>xpath_exists</function>, which evaluate XPath 1.0
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expressions.
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</para>
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<synopsis>
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<function>xpath</function>(<replaceable>xpath</replaceable>, <replaceable>xml</replaceable><optional>, <replaceable>nsarray</replaceable></optional>)
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<function>xpath</function>(<replaceable>xpath</replaceable>, <replaceable>xml</replaceable> <optional>, <replaceable>nsarray</replaceable></optional>)
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</synopsis>
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<para>
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The function <function>xpath</function> evaluates the XPath
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expression <replaceable>xpath</replaceable> against the XML value
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expression <replaceable>xpath</replaceable> (a <type>text</> value)
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against the XML value
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<replaceable>xml</replaceable>. It returns an array of XML values
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corresponding to the node set produced by the XPath expression.
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</para>
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@ -8657,13 +8659,13 @@ SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Tor
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</para>
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<para>
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The third argument of the function is an array of namespace
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mappings. This array should be a two-dimensional array with the
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length of the second axis being equal to 2 (i.e., it should be an
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The optional third argument of the function is an array of namespace
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mappings. This array should be a two-dimensional <type>text</> array with
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the length of the second axis being equal to 2 (i.e., it should be an
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array of arrays, each of which consists of exactly 2 elements).
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The first element of each array entry is the namespace name (alias), the
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second the namespace URI. It is not required that aliases provided in
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this array are the same that those being used in the XML document itself (in
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this array be the same as those being used in the XML document itself (in
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other words, both in the XML document and in the <function>xpath</function>
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function context, aliases are <emphasis>local</>).
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</para>
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@ -8671,7 +8673,7 @@ SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Tor
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<para>
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Example:
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<screen><![CDATA[
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SELECT xpath('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
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SELECT xpath('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
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ARRAY[ARRAY['my', 'http://example.com']]);
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xpath
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@ -8682,7 +8684,7 @@ SELECT xpath('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
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</para>
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<para>
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How to deal with default (anonymous) namespaces:
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To deal with default (anonymous) namespaces, do something like this:
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<screen><![CDATA[
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SELECT xpath('//mydefns:b/text()', '<a xmlns="http://example.com"><b>test</b></a>',
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ARRAY[ARRAY['mydefns', 'http://example.com']]);
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@ -8691,6 +8693,36 @@ SELECT xpath('//mydefns:b/text()', '<a xmlns="http://example.com"><b>test</b></a
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--------
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{test}
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(1 row)
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]]></screen>
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</para>
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<indexterm>
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<primary>xpath_exists</primary>
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</indexterm>
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<synopsis>
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<function>xpath_exists</function>(<replaceable>xpath</replaceable>, <replaceable>xml</replaceable> <optional>, <replaceable>nsarray</replaceable></optional>)
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</synopsis>
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<para>
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The function <function>xpath_exists</function> is a specialized form
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of the <function>xpath</function> function. Instead of returning the
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individual XML values that satisfy the XPath, this function returns a
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boolean indicating whether the query was satisfied or not. This
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function is equivalent to the standard <literal>XMLEXISTS</> predicate,
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except that it also offers support for a namespace mapping argument.
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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 xpath_exists('/my:a/text()', '<my:a xmlns:my="http://example.com">test</my:a>',
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ARRAY[ARRAY['my', 'http://example.com']]);
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xpath_exists
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--------------
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t
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(1 row)
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]]></screen>
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</para>
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</sect2>
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@ -8698,7 +8730,7 @@ SELECT xpath('//mydefns:b/text()', '<a xmlns="http://example.com"><b>test</b></a
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<sect2 id="functions-xml-mapping">
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<title>Mapping Tables to XML</title>
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<indexterm zone="functions-xml-mapping">
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<indexterm zone="functions-xml-mapping">
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<primary>XML export</primary>
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</indexterm>
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