[xquery-talk] outer join between 2 sequences

Adam Retter adam.retter at googlemail.com
Sun Sep 28 04:32:42 PDT 2014

> I have sequence A consisting of the numbers 0 to 4000000 and sequnce B
> consisting of about 100k random I numbers within the range of sequence A and
> I want the outer join where sequence B is "null".

There is no 'null' in XQuery, so I am not quite sure what you mean
here. If you ware looking for all values that appear in sequence A and
sequence B, then you can do the following -

$a[. = $b]

> Should one expect bad performance in sequence B is not sorted and can one
> expect reasonable performance if it is?

I think that question is very implementation specific. If all of your
data is in RAM, as your dataset is relatively small and these are just
numbers, I would expect performance to be excellent. I am not sure
that sorting will make much of a difference, but it depends on the
implementation and how it initiates the search for a false comparison
in a large sequence.

> I am guessing that performance will vary by implemetation.

Of course!

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Adam Retter

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