Re: [xsl] Performance of xsl:for-each with key() lookup

["David Carlisle d.p.carlisle@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

On Wed, 26 Sep 2018 at 23:07, Michael Kay mike@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Shame that the download link no longer works. And I'm not sure I've got an
archive version either, I think I was assuming at the time that putting things
on the web gave them permanence.


the doc (but not the software zip file) I think is in the internet
archive, for example this 1999 snapshot


https://web.archive.org/web/19990220013518/http://home.iclweb.com/icl2/mhkay/
saxon.html


>
> I do remember that the early attempts at streaming gave me no end of
trouble, and were soon abandoned. The analysis of what was streamable and what
wasn't was hopelessly fragile.
>
> Michael Kay
> Saxonica
>
> > On 26 Sep 2018, at 22:50, Wendell Piez wapiez@xxxxxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hey Alan, check out version 4, I'm sure Mike Kay doesn't remember the
> > details of that one either --
> >
> > https://markmail.org/message/bapqkmmd7bz2fxce
> >
> > Probably wasn't providing late variable binding.
> >
> > Still giving great value! So far we have come!
> >
> > Cheers, Wendell
> >
> > On Wed, Sep 26, 2018 at 5:01 PM Alan Painter alan.painter@xxxxxxxxx
> > <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>
> >> 10 years old and still giving great value.
> >>
> >> On Wed, Sep 26, 2018, 22:54 Michael Kay mike@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>>
> >>> The answer obviously depends on the processor.
> >>>
> >>> With Saxon, if a variable is only referenced once, and the reference
isn't in a loop, then it will be inlined. So if you write
> >>>
> >>>>  <xsl:variable name="elems" select="key('some', $value, $doc)"
> >>>> as="element()*"/>
> >>>>   <xsl:for-each select="$elems">
> >>>
> >>> then Saxon will rewrite it as
> >>>
> >>>> <xsl:for-each select="key('some', $value, $doc)">
> >>>
> >>> The main benefit of this rewrite is better pipelining. A variable causes
the list of items to be stored somewhere in memory; without the variable, each
item is processed as soon as it is found.
> >>>
> >>> Michael Kay
> >>> Saxonica
> >>>
> >>> PS: Saxon 9.1 is about 10 years ago, so my memory of it is rather
rusty.
> >>>
> >>>
> >>>> On 26 Sep 2018, at 21:40, Martynas JuseviD
ius martynas@xxxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> I'm using the following pattern in multiple places in my stylesheets:
> >>>>
> >>>>   <xsl:for-each select="key('some', $value, $doc)">
> >>>>
> >>>> My question is, would iteration be optimized if I selected the nodes
> >>>> into a variable first?
> >>>>
> >>>>   <xsl:variable name="elems" select="key('some', $value, $doc)"
> >>>> as="element()*"/>
> >>>>   <xsl:for-each select="$elems">
> >>>>
> >>>> I guess it should be faster if the key() function is called only once
> >>>> instead of multiple times? But if there is an index maybe it doesn't
> >>>> matter?
> >>>>
> >>>> And does the same apply to
> >>>>
> >>>>   <xsl:apply-templates select="key('some', $value, $doc)"/>
> >>>>
> >>>> as well?
> >>>>
> >>>> I'm using Saxon 9.1.0.8.
> >>>>
> >>>>
> >>>> Martynas
> >>>>
> >>>
> >> XSL-List info and archive
> >> EasyUnsubscribe (by email)
> >
> >
> >
> > --
> > Wendell Piez | http://www.wendellpiez.com
> > XML | XSLT | electronic publishing
> > Eat Your Vegetables
> > _____oo_________o_o___ooooo____ooooooo_^