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Re: Does the count() function require access to the wh

Subject: Re: Does the count() function require access to the whole subtree?
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxx>
Date: Thu, 16 Jan 2014 10:31:04 -0500
Re:  Does the count() function require access to the wh

Just a question prompted by David's commentary:

On Thu, Jan 16, 2014 at 6:44 AM, David Carlisle <davidc@xxxxxxxxx> wrote:
> Some operations are intrinsically not streamable, if you replace data()
> by reverse() for example then reverse(//x) is going to have to buffer
> every node somewhere and return the x elements in reverse order so since
> it has to return the last one first the operation can't be streamed in
> any reasonable way irrespective of the input sequence, which happens to
> be //x here. So nesting of x would not be relevant.

I imagine that even in this case, streaming might not be completely
useless when used within a pipeline.

For example, your pipeline could collect all //x (streaming) and then
reverse them (not streaming).

In principle, you would need only the memory for holding //x (or
rather, copies of //x or pointers to them), not the entire collection
within which they are found.

This is correct, isn't it? I imagine the general principle here is
that pipelining and streaming play well together.

I also had a related question, back in September. It wasn't answered
(rare for this list), either because it wasn't clear, or because XML
Summer School was going on at the time. Or both.


Cheers, Wendell

Wendell Piez | http://www.wendellpiez.com
XML | XSLT | electronic publishing
Eat Your Vegetables

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