[xquery-talk] Deep-equal between sequences
Ronald Bourret
rpbourret at rpbourret.com
Wed Jul 11 00:38:54 PDT 2007
Hello,
I have two sequences that I would like to compare. The sequences are
composed of elements and the comparison is true if any member of the
first sequence is deep-equal to any member of the second sequence.
(Essentially, I want to do an = operation, but using deep-equal rather
than atomic equality.)
Can anybody think of a way to do this comparison with the = operator?
This would give the query engine the chance to optimize the comparison,
or at least to end the comparison early if a match was found. The
problem is somewhat simplified by the fact that the definition of the
elements is <!ELEMENT A (A1, A2)>.
Note that the following is not sufficient:
let $firstSeq := ...
let $secondSeq := ...
return
if (($firstSeq/A1 = $secondSeq/A1) and
($firstSeq/A2 = $secondSeq/A2)
then fn:true()
else fn:false()
The problem with this is that it returns true if any pairs of A1 and A2
match, while I require that an A1 and A2 with the same parent in the
first sequence match an A1 and A2 with the same parent in the second
sequence.
Barring use of the = operator, is there a simple solution to this
problem that would allow the engine to stop processing on the first
match, rather than performing n x m deep-equal comparisons and searching
the resulting sequence for an instance of true?
Thanks in advance,
-- Ron
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