Re: xpath() subquery for empty array

Scott Bailey wrote:
> 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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Thanks Scott but that throws up a syntax error (at the closing bracket
of array[]):

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

-- Roy