Re: BUG #4024: xpath() results lose namespace mappings - Mailing list pgsql-bugs

Would someone please comment on this bug report from March, 2008?

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Matt Magoffin wrote:
>
> The following bug has been logged online:
>
> Bug reference:      4024
> Logged by:          Matt Magoffin
> Email address:      postgresql.org@msqr.us
> PostgreSQL version: 8.3.0
> Operating system:   OS X 10.5, Windows XP
> Description:        xpath() results lose namespace mappings
> Details:
>
> I was trying to extract XML fragments within a pl/pgsql function by nested
> xpath() function calls, and found that when namespaces are used in the
> XML, only the first xpath() call is able to correctly use namespaces.
>
> First here is an example that works, when no namespaces are used:
>
> BEGIN;
> CREATE TEMPORARY TABLE tmp_xpath_test (x xml) ON COMMIT DROP;
> INSERT INTO tmp_xpath_test VALUES (
>     '<foo><bar x="y">bar1</bar><bar x="y">bar2</bar></foo>'::xml);
> SELECT (xpath('/foo/bar[1]', t.x))[1] FROM tmp_xpath_test t;
> SELECT xpath('/bar/@x', (xpath('/foo/bar[1]', t.x))[1]) FROM
> tmp_xpath_test t;
> COMMIT;
>
> The first select is just there to show the result of the inner call to
> xpath() in the second select, and the second select returns:
>
> SELECT xpath('/bar/@x', (xpath('/foo/bar[1]', t.x))[1]) FROM
> tmp_xpath_test t;
> xpath
> -------
> {y}
> (1 row)
>
> Now if I use XML with namespaces, the first SELECT works, but the second
> never returns the expected results:
>
> BEGIN;
> CREATE TEMPORARY TABLE tmp_xpath_test (x xml) ON COMMIT DROP;
> INSERT INTO tmp_xpath_test VALUES (
>     '<a:foo xmlns:a="a:urn"><a:bar x="y">bar1</a:bar><a:bar
> x="y">bar2</a:bar></a:foo>'::xml);
> SELECT (xpath('/a:foo/a:bar[1]', t.x, ARRAY[ARRAY['a','a:urn']]))[1] FROM
> tmp_xpath_test t;
> SELECT xpath('/a:bar/@x', (xpath('/a:foo/a:bar[1]', t.x,
> ARRAY[ARRAY['a','a:urn']]))[1],
>     ARRAY[ARRAY['a','a:urn']]) FROM tmp_xpath_test t;
> COMMIT;
>
> The select results are
>
> SELECT (xpath('/a:foo/a:bar[1]', t.x, ARRAY[ARRAY['a','a:urn']]))[1] FROM
> tmp_xpath_test t;
>           xpath
> ---------------------------
> <a:bar x="y">bar1</a:bar>
> (1 row)
>
> SELECT xpath('/a:bar/@x', (xpath('/a:foo/a:bar[1]', t.x,
> ARRAY[ARRAY['a','a:urn']]))[1],
> lms_kia(> ARRAY[ARRAY['a','a:urn']]) FROM tmp_xpath_test t;
> xpath
> -------
> {}
> (1 row)
>
> For the second select, I expected a single XML text node containing "y",
> just like from the no-namespace result.
>
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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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