[xquery-talk] From map entry pairs to a pair of arrays

W.S. Hager wshager at gmail.com
Mon Jul 17 02:10:01 PDT 2017

What I meant is that the cost of immutability can be avoided in some cases.
That's primarily a matter of low level short-circuiting, not so much of
writing something new. I don't know if this can be done in Java, I know the
Clojure compiler does this, and I'm not aware of XQ engines that do
transient operations on persistent collections.

Op 16 jul. 2017 23:58 schreef "Michael Kay" <mike at saxonica.com>:

ce between C and Assembly is a lot smaller than between C and XQ, and I
think memory management should not be taken lightly (I'm not saying you
do). In OP's case, I believe keys could be discarded while memory layout
remains intact.

As a general rule of thumb, a lower-level language performs better provided
that you have the time and skills to write the code efficiently.

And as a general rule of thumb, you don't.

Even when you are quite convinced that you do.

It's a long time since I wrote in anything as low-level as C or assembler,
but if you compare XQuery and Java, the level of abstraction of the API for
maps is very similar, so there is no intrinsic reason to believe one should
perform better than the other. The main difference is that maps in XQuery
are immutable, which means you pay a little more for some operations (like
adding a new entry), and you pay a lot less for other operations (llike
bulk copying).

Michael Kay
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