xpath() subquery for empty array

[Roy Walter <walt@xxxxxxxxxxxxxxxx>]

In postgres 8.4 When running xpath() queries it seems that empty results are always returned. So if I query a table containing 1000 XML documents a 1000 rows will always be fetched even if the xpath() element of the query only matches 10 documents.

The documentation states:

The function xpath evaluates the XPath _expression_ xpath against the XML value xml. It returns an array of XML values corresponding to the node set produced by the XPath _expression_.

Yet it seems that empty node sets (arrays) are also returned. So, my thought was to run a subquery to eliminate empty arrays, e.g.:

SELECT x
FROM (SELECT xpath('//entry[contains(p, ''searchtext'')]/@*', docxml)
AS x FROM docs) AS y WHERE x <> [test for empty array?????????]

How do I test for an empty array in postgres?

Thanks in advance,
Roy