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 2010-08-08 19:15:27 +00:00
parent 46aa77c7bd
commit 4dfc457854
8 changed files with 205 additions and 39 deletions

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

View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.99 2010/08/05 04:21:54 petere Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.100 2010/08/08 19:15:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -3541,3 +3541,27 @@ Datum xmlexists(PG_FUNCTION_ARGS)
return 0;
#endif
}
/*
* Determines if the node specified by the supplied XPath exists
* in a given XML document, returning a boolean. Differs from
* xmlexists as it supports namespaces and is not defined in SQL/XML.
*/
Datum
xpath_exists(PG_FUNCTION_ARGS)
{
#ifdef USE_LIBXML
text *xpath_expr_text = PG_GETARG_TEXT_P(0);
xmltype *data = PG_GETARG_XML_P(1);
ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
int res_nitems;
xpath_internal(xpath_expr_text, data, namespaces,
&res_nitems, NULL);
PG_RETURN_BOOL(res_nitems > 0);
#else
NO_XML_SUPPORT();
return 0;
#endif
}

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@ -37,7 +37,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.592 2010/08/08 16:27:04 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.593 2010/08/08 19:15:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201008071
#define CATALOG_VERSION_NO 201008081
#endif

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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.576 2010/08/08 16:27:04 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.577 2010/08/08 19:15:27 tgl Exp $
*
* NOTES
* The script catalog/genbki.pl reads this file and generates .bki
@ -4415,6 +4415,11 @@ DESCR("evaluate XPath expression");
DATA(insert OID = 2614 ( xmlexists PGNSP PGUID 12 1 0 0 f f f t f i 2 0 16 "25 142" _null_ _null_ _null_ _null_ xmlexists _null_ _null_ _null_ ));
DESCR("test XML value against XPath expression");
DATA(insert OID = 3049 ( xpath_exists PGNSP PGUID 12 1 0 0 f f f t f i 3 0 16 "25 142 1009" _null_ _null_ _null_ _null_ xpath_exists _null_ _null_ _null_ ));
DESCR("test XML value against XPath expression, with namespace support");
DATA(insert OID = 3050 ( xpath_exists PGNSP PGUID 14 1 0 0 f f f t f i 2 0 16 "25 142" _null_ _null_ _null_ _null_ "select pg_catalog.xpath_exists($1, $2, ''{}''::pg_catalog.text[])" _null_ _null_ _null_ ));
DESCR("test XML value against XPath expression");
/* uuid */
DATA(insert OID = 2952 ( uuid_in PGNSP PGUID 12 1 0 0 f f f t f i 1 0 2950 "2275" _null_ _null_ _null_ _null_ uuid_in _null_ _null_ _null_ ));
DESCR("I/O");

View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.32 2010/08/05 04:21:54 petere Exp $
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.33 2010/08/08 19:15:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -37,6 +37,7 @@ extern Datum texttoxml(PG_FUNCTION_ARGS);
extern Datum xmltotext(PG_FUNCTION_ARGS);
extern Datum xmlvalidate(PG_FUNCTION_ARGS);
extern Datum xpath(PG_FUNCTION_ARGS);
extern Datum xpath_exists(PG_FUNCTION_ARGS);
extern Datum xmlexists(PG_FUNCTION_ARGS);
extern Datum table_to_xml(PG_FUNCTION_ARGS);

View File

@ -502,7 +502,7 @@ SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
{<b>two</b>,<b>etc</b>}
(1 row)
-- Test xmlexists evaluation
-- Test xmlexists and xpath_exists
SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>');
xmlexists
-----------
@ -515,6 +515,18 @@ SELECT xmlexists('//town[text() = ''Cwmbran'']' PASSING BY REF '<towns><town>Bid
t
(1 row)
SELECT xpath_exists('//town[text() = ''Toronto'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
xpath_exists
--------------
f
(1 row)
SELECT xpath_exists('//town[text() = ''Cwmbran'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
xpath_exists
--------------
t
(1 row)
INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
INSERT INTO xmltest VALUES (5, '<menu><beers><name>Molson</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
INSERT INTO xmltest VALUES (6, '<myns:menu xmlns:myns="http://myns.com"><myns:beers><myns:name>Budvar</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
@ -543,6 +555,42 @@ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molso
1
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beer',data);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers',data);
count
-------
2
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers/name[text() = ''Molson'']',data);
count
-------
1
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beer',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
2
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers/myns:name[text() = ''Molson'']',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
1
(1 row)
CREATE TABLE query ( expr TEXT );
INSERT INTO query VALUES ('/menu/beers/cost[text() = ''lots'']');
SELECT COUNT(id) FROM xmltest, query WHERE xmlexists(expr PASSING BY REF data);

View File

@ -456,7 +456,7 @@ LINE 1: SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>'...
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
-- Test xmlexists evaluation
-- Test xmlexists and xpath_exists
SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>');
ERROR: unsupported XML feature
LINE 1: ...sts('//town[text() = ''Toronto'']' PASSING BY REF '<towns><t...
@ -469,6 +469,18 @@ LINE 1: ...sts('//town[text() = ''Cwmbran'']' PASSING BY REF '<towns><t...
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
SELECT xpath_exists('//town[text() = ''Toronto'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
ERROR: unsupported XML feature
LINE 1: ...ELECT xpath_exists('//town[text() = ''Toronto'']','<towns><t...
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
SELECT xpath_exists('//town[text() = ''Cwmbran'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
ERROR: unsupported XML feature
LINE 1: ...ELECT xpath_exists('//town[text() = ''Cwmbran'']','<towns><t...
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
ERROR: unsupported XML feature
LINE 1: INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</n...
@ -517,6 +529,42 @@ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molso
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beer',data);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers',data);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers/name[text() = ''Molson'']',data);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beer',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
0
(1 row)
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers/myns:name[text() = ''Molson'']',data,ARRAY[ARRAY['myns','http://myns.com']]);
count
-------
0
(1 row)
CREATE TABLE query ( expr TEXT );
INSERT INTO query VALUES ('/menu/beers/cost[text() = ''lots'']');
SELECT COUNT(id) FROM xmltest, query WHERE xmlexists(expr PASSING BY REF data);

View File

@ -164,21 +164,29 @@ SELECT xpath('//text()', '<local:data xmlns:local="http://127.0.0.1"><local:piec
SELECT xpath('//loc:piece/@id', '<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc', 'http://127.0.0.1']]);
SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
-- Test xmlexists evaluation
-- Test xmlexists and xpath_exists
SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>');
SELECT xmlexists('//town[text() = ''Cwmbran'']' PASSING BY REF '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>');
SELECT xpath_exists('//town[text() = ''Toronto'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
SELECT xpath_exists('//town[text() = ''Cwmbran'']','<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'::xml);
INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
INSERT INTO xmltest VALUES (5, '<menu><beers><name>Molson</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
INSERT INTO xmltest VALUES (6, '<myns:menu xmlns:myns="http://myns.com"><myns:beers><myns:name>Budvar</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
INSERT INTO xmltest VALUES (7, '<myns:menu xmlns:myns="http://myns.com"><myns:beers><myns:name>Molson</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer' PASSING data);
SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer' PASSING BY REF data BY REF);
SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers' PASSING BY REF data);
SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molson'']' PASSING BY REF data);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beer',data);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers',data);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/menu/beers/name[text() = ''Molson'']',data);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beer',data,ARRAY[ARRAY['myns','http://myns.com']]);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers',data,ARRAY[ARRAY['myns','http://myns.com']]);
SELECT COUNT(id) FROM xmltest WHERE xpath_exists('/myns:menu/myns:beers/myns:name[text() = ''Molson'']',data,ARRAY[ARRAY['myns','http://myns.com']]);
CREATE TABLE query ( expr TEXT );
INSERT INTO query VALUES ('/menu/beers/cost[text() = ''lots'']');
SELECT COUNT(id) FROM xmltest, query WHERE xmlexists(expr PASSING BY REF data);