mirrors/postgres
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Set correct context for XPath evaluation

Browse Source 
According to the SQL standard, the context of XMLTABLE's XPath
row_expression is the document node of the XML input document, not the
root node.  This becomes visible when a relative path rather than
absolute is used as row expression.  Absolute paths is what was used in
original tests and docs (and the most common form used in examples
throughout the interwebs), which explains why this wasn't noticed
before.

Other functions such as xpath() and xpath_exists() also have this
problem.  While not specified by the SQL standard, it would be pretty
odd to leave those functions to behave differently than XMLTABLE, so
change them too.  However, this is a backwards-incompatible change.

No backpatch, out of fear of breaking code depending on the original
broken behavior.

Author: Markus Winand
Reported-By: Markus Winand
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/0684A598-002C-42A2-AE12-F024A324EAE4@winand.at
This commit is contained in:
Alvaro Herrera 2018-06-21 15:56:11 -04:00
parent 425b4c082c
commit e474c2b7e4
5 changed files with 27 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
src/backend/utils/adt/xml.c
View File

@ -3934,10 +3934,7 @@ xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
if (xpathctx == NULL || xmlerrcxt->err_occurred)
xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
"could not allocate XPath context");
xpathctx->node = xmlDocGetRootElement(doc);
if (xpathctx->node == NULL || xmlerrcxt->err_occurred)
xml_ereport(xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
"could not find root XML element");
xpathctx->node = (xmlNodePtr) doc;
/* register namespaces, if any */
if (ns_count > 0)
@ -4276,10 +4273,7 @@ XmlTableSetDocument(TableFuncScanState *state, Datum value)
if (xpathcxt == NULL || xtCxt->xmlerrcxt->err_occurred)
xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
"could not allocate XPath context");
xpathcxt->node = xmlDocGetRootElement(doc);
if (xpathcxt->node == NULL || xtCxt->xmlerrcxt->err_occurred)
xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_INTERNAL_ERROR,
"could not find root XML element");
xpathcxt->node = (xmlNodePtr) doc;
}
PG_CATCH();
{

8
src/test/regress/expected/xml.out
View File

@ -670,6 +670,12 @@ SELECT xpath('/nosuchtag', '<root/>');
{}
(1 row)
SELECT xpath('root', '<root/>');
xpath
-----------
{<root/>}
(1 row)
-- Round-trip non-ASCII data through xpath().
DO $$
DECLARE
@ -1212,7 +1218,7 @@ SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaa
SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaaa?> <!--z--> bbbb<x>xxx</x>cccc</element></root>' COLUMNS element text PATH 'element/text()'); -- should fail
ERROR: more than one value returned by column XPath expression
-- CDATA test
select * from xmltable('r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
select * from xmltable('d/r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
c
-------------------------
<hello> &"<>!<a>foo</a>

12
src/test/regress/expected/xml_1.out
View File

@ -576,6 +576,12 @@ LINE 1: SELECT xpath('/nosuchtag', '<root/>');
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
SELECT xpath('root', '<root/>');
ERROR: unsupported XML feature
LINE 1: SELECT xpath('root', '<root/>');
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
-- Round-trip non-ASCII data through xpath().
DO $$
DECLARE
@ -1067,10 +1073,10 @@ LINE 1: SELECT * FROM xmltable('/root' passing '<root><element>a1a<!...
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
-- CDATA test
select * from xmltable('r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
select * from xmltable('d/r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
ERROR: unsupported XML feature
LINE 1: select * from xmltable('r' passing '<d><r><c><![CDATA[<hello...
^
LINE 1: select * from xmltable('d/r' passing '<d><r><c><![CDATA[<hel...
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
-- XML builtin entities

8
src/test/regress/expected/xml_2.out
View File

@ -650,6 +650,12 @@ SELECT xpath('/nosuchtag', '<root/>');
{}
(1 row)
SELECT xpath('root', '<root/>');
xpath
-----------
{<root/>}
(1 row)
-- Round-trip non-ASCII data through xpath().
DO $$
DECLARE
@ -1192,7 +1198,7 @@ SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaa
SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaaa?> <!--z--> bbbb<x>xxx</x>cccc</element></root>' COLUMNS element text PATH 'element/text()'); -- should fail
ERROR: more than one value returned by column XPath expression
-- CDATA test
select * from xmltable('r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
select * from xmltable('d/r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
c
-------------------------
<hello> &"<>!<a>foo</a>

3
src/test/regress/sql/xml.sql
View File

@ -188,6 +188,7 @@ SELECT xpath('count(//*)=0', '<root><sub/><sub/></root>');
SELECT xpath('count(//*)=3', '<root><sub/><sub/></root>');
SELECT xpath('name(/*)', '<root><sub/><sub/></root>');
SELECT xpath('/nosuchtag', '<root/>');
SELECT xpath('root', '<root/>');
-- Round-trip non-ASCII data through xpath().
DO $$
@ -423,7 +424,7 @@ SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaa
SELECT * FROM xmltable('/root' passing '<root><element>a1a<!-- aaaa -->a2a<?aaaaa?> <!--z--> bbbb<x>xxx</x>cccc</element></root>' COLUMNS element text PATH 'element/text()'); -- should fail
-- CDATA test
select * from xmltable('r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
select * from xmltable('d/r' passing '<d><r><c><![CDATA[<hello> &"<>!<a>foo</a>]]></c></r><r><c>2</c></r></d>' columns c text);
-- XML builtin entities
SELECT * FROM xmltable('/x/a' PASSING '<x><a><ent>&apos;</ent></a><a><ent>&quot;</ent></a><a><ent>&amp;</ent></a><a><ent>&lt;</ent></a><a><ent>&gt;</ent></a></x>' COLUMNS ent text);