[xquery-talk] Release of the GCX XQuery EngineQ

Florent Georges darkman_spam at yahoo.fr
Mon Feb 5 10:34:00 PST 2007

Michael Kay wrote:


> In turn this means that if a query does doc($x) and
> doc($y), you can't safely avoid building the tree unless
> you can prove that $x and $y will be different URIs (or,
> perhaps, that the identity of the nodes makes no
> difference to the outcome). This is the kind of corner
> case that makes optimization in practice much harder than
> it is in academic theory: you're not allowed to do an
> optimization that benefits 99.99% of queries if it causes
> incorrect results for the other 0.01%.

  You cannot make this kind of optimization the default.
But you can say "ok, if you know what you do, you can
activate this optimization for your queries", by providing
the ability to set an option or whatever, isn't it?  Even
without trying to detect if the queries will be right then
(but it is better, sure).




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