Re: [xsl] improving performance in creating ids

Subject: Re: [xsl] improving performance in creating ids
From: "Pieter Lamers pieter.lamers@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 23 Apr 2019 22:02:13 -0000
Hi Wendell, Mike and Martin,

Thanks for your replies. I've seen now that xsl:number can be indeed most helpful (bringing one minute down to half a second). I am still struggling with the from pattern, as I need it to renumber by ancestor having @id, and I do not know how to write that.

B B B B B B B B B  <xsl:number level="any" from="*[@id]"/>
incorrectly renumbers also if there are siblings with an @id.

from="ancestor::*[@id]" returns an error.

Now for some sleep.

Best to all,

On 23/04/2019 23:32, Wendell Piez wapiez@xxxxxxxxxxxxxxx wrote:
Hey Pieter,

If performance were the issue, I might try factoring out the ID
labeling into a completely separate pass, in order (for example) to
implement it as a sibling traversal, passing parameters forward to
increment the ID values. (If your numbering is fancy, for example
scoping the increment to the element type as well as the ancestor, you
might have to pass a map forward.) I think that ought to be pretty
fast, plus it separates this logic from the other logic of the XSLT.
It's essentially like treating the XSLT engine like an overpowered SAX
parser. (Not that I would know how to make one of those.)

But this is only if xsl:number wasn't doing it, after I tried
something like what Martin H shows with plain old templates.

<xsl:variable name="ilk" select="local-name()"/>
<xsl:value-of select="$ilk || '-'"/>
<xsl:number level="any" from="*[@id]" count="*[local-name() eq $ilk]"/>

-- untested --

Cheers, Wendell

On Tue, Apr 23, 2019 at 10:57 AM Martin Honnen martin.honnen@xxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
On 23.04.2019 16:28, Pieter Lamers pieter.lamers@xxxxxxxxxxxx wrote:

Thanks for your quick reply. the node identity comparison helped quite a
bit, although I am still around a minute for a full book of ids. I am
not sure how xsl:number would help here, and what kind of performance
win it would give over count(). I tried something with a nested
transformation, but what should I feed it?

      <xsl:number select="*[last()]"/>
works (given a set of preceding nodes) but it is slightly slower than a
count() in the xquery. Maybe I should be using xsl:number differently?

It is difficult for me to suggest that without knowing the XML input structure and whether you want to generate that id based on a count or numbering only for certain nodes or some particular element type. In general if I wanted to delegate counting to xsl:number similar to your function I would define a template in a mode for that e.g.

     <xsl:template match="*" mode="number">
        <xsl:number level="any" from="*[@id]"/>

and then, where you need that number, you would use e.g.

<xsl:apply-templates select="." mode="number"/>

Both the template or the or the select of the apply-templates can of
course be adapted to more particular needs.

As for being more efficient that using count, that then depends on the
implementation but I would think there is some optimization to be
expected in an XSLT processor for xsl:number.

Pieter Lamers
John Benjamins Publishing Company
Postal Address: P.O. Box 36224, 1020 ME AMSTERDAM, The Netherlands
Visiting Address: Klaprozenweg 75G, 1033 NN AMSTERDAM, The Netherlands
Warehouse: Kelvinstraat 11-13, 1446 TK PURMEREND, The Netherlands
tel: +31 20 630 4747

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