Robert Haas wrote:
On Sun, Jun 27, 2010 at 12:04 PM, Mike Fowler <m...@mlfowler.com> wrote:
Thanks again for your help Robert, turns out the fault was in the pg_proc
entry (the 3 up there should've been a two!). Once I took the grammar out it
was quickly obvious where I'd gone wrong.
Glad it was a helpful suggestion.
Attached is a patch with the revised XMLEXISTS function, complete with
grammar support and regression tests. The implemented grammar is:
XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] )
Though the full grammar makes everything after the xpath_expression
optional, I've left it has mandatory simply to avoid lots of rework of the
function (would need new null checks, memory handling would need reworking).
So if you don't specify the xml_value, what does the xpath_expression
get applied to?
From what I can gather the xpath_expression would be evalutated against
an empty document thereby returning false for every xpath_expression
except for 'true()'. Apache Derby has made the xml_value mandatory as
well (though I'll stress my conclusion wasn't based on this fact). If
you think it would better to adhere more closely to the standard I can
certainly look to do so. From a cursory glance at libxml's API I think
it should be straight forward to query against an empty document such
that I wouldn't need ot code for the exceptional case (or cases if I've
missed others).
Regards,
--
Mike Fowler
Registered Linux user: 379787
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