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
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