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 14:28:32 -0000
Hi Martin,

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?

B B B <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?

however, your suggestion of nesting transformations also opens the door to using generate-id() in the xquery realm, with a nested transformation, thereby sidestepping the problem that eXist returns something different for generate-id() from Saxon (also in reply toB Dave Pawson).

I will see where that gets me.


On 23/04/2019 14:19, Martin Honnen martin.honnen@xxxxxx wrote:
On 23.04.2019 14:07, Pieter Lamers pieter.lamers@xxxxxxxxxxxx wrote:
Hi All,

I need generated-ids on elements in a BITS file that have @rids, so I
can link back to them. I cannot use generate-id(), because I need it to
produce the same id in both the xquery (eXist) context and in the XSL
(saxon) contect.

I have created a function that will generate a human readable id based
on the id of the nearest ancestor/@id and then element-name + sequence
number. It produces the output that I like, but at the cost of a poor
performance (when run on a whole book) . now with the preceding/ancestor
juggling that I do there might be a better way than mine, so my question
is if there is a better way to tackle this problem.

My function:

declare function local:get-id-in-doc ( $target as element() ) as xs:string
B B let $current-element as xs:string := local-name($target)
B B let $ancestor-with-id as element()? := $target/ancestor::*[@id][1]
B B let $prefix as xs:string? := $ancestor-with-id/@id/string()

B B  let $count :=
B B B B  if($prefix) then
B B B B B B  (: case 1: there is an ancestor with an @id :)
B B B B B B  count($target/preceding::*[local-name() eq
$current-element][ancestor::* = $ancestor-with-id]) + 1

That general value comparison

B ancestor::* = $ancestor-with-id

looks odd, shouldn't that be

B ancestor::*[. is $ancestor-with-id]

? I would expect node identity comparison and not value comparison.

Whether that improves performance and then also on two different
implementations is something I can't tell without testing.

2. Is there an alternative way of generating ids (possibly having less
human-readable values) that would work in both the xquery and xslt realm?

It looks like a job for XSLT's xsl:number and I wonder whether your database xquery processor doesn't provide a way to simply run an XSLT transformation.

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