Re: Add XMLNamespaces to XMLElement

[newtglobal postgresql_contributors]

The following review has been posted through the commitfest application:
make installcheck-world:  not tested
Implements feature:       not tested
Spec compliant:           not tested
Documentation:            not tested

Hi Pavel,

I have tested this patch, and it proves to be highly useful when handling 
XMLNAMESPACES() with both DEFAULT and NO DEFAULT options. The following test 
cases confirm its correctness:


SELECT xmlelement(
    NAME "foo",
    XMLNAMESPACES('http://x.y' AS xy, 'http://a.b' AS ab, DEFAULT 'http://d.e'),
    xmlelement(NAME "foot", 
        xmlelement(NAME "xy:shoe"), 
        xmlelement(NAME "ab:lace")
    )
);

SELECT xmlelement(
    NAME "foo",
    XMLNAMESPACES('http://x.y' AS xy, 'http://a.b' AS ab, NO DEFAULT),
    xmlelement(NAME "foot", 
        xmlelement(NAME "xy:shoe"), 
        xmlelement(NAME "ab:lace")
    )
);
Additionally, I verified that the patch correctly supports multiple namespaces 
when using both DEFAULT and NO DEFAULT, ensuring expected behavior across 
different use cases.

Great work on this improvement!