How to check if an array is empty

Hi,

in my special case I'd like to check if a XML[] is empty, because postgres
doesn't implement any equality operators, this is not a 'simple' task.

My current solution is:

SELECT * FROM sometable WHERE XMLSERIALIZE(CONTENT ((XPATH('/a:bar,
somexmlcolumn, ARRAY[ARRAY['a', 'http://foo]]))[1]) AS text)<>''

But there must be a better way - maybe I missed something important - I also
tried queries like the following:

SELECT * FROM sometable WHERE (XPATH('/a:bar', somexmlcolumn,
ARRAY[ARRAY['a', 'http://foo']]))<>('{}'::XML[])

Any ideas and feedback are welcome.

Cheers, Tobias