Re: xpath() subquery for empty array

Roy Walter wrote:

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

WHERE x != array[]::xml[]

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ERROR:  syntax error at or near "]"
LINE 3: AS x FROM docs) AS y WHERE x != array[]::xml[]
                                              ^