Peter Eisentraut schrieb am 12.03.2018 um 23:31:
I am not sure if this qualifies as a bug: query_to_xml() returns an empty XML document when the query returns no rows, e.g: select query_to_xml('select 42 where false', false, true, ''); The problem with this is, that if the resulting XML is then fed into e.g. the xpath() function, that function fails because the "empty" document is an invalid XML:That's because you have the tableforest argument set to true. If you want a proper XML document, then you should write select query_to_xml('select 42 where false', false, false, '');
Hmm, that indeed works. I didn't want the extra level introduced by the <table> tag, that's why I used tableforest = true. But that's easier to deal with than the check for an invalid document I still think it's incorrect to return an empty (=invalid) XML instead of a NULL value though. Regards Thomas
