Re: XQuery/XPath 3.1: Node List to Node Set ("distinct

On Wed, Dec 29, 2021 at 11:10 AM Martin Honnen martin.honnen@xxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> As I said, eXist-db is struggling
>   with generate-id based approaches, at least if nodes from different
>   document (fragments?) are involved.

Yes, bugs happen...

Just trying to evaluate Dr. Kay's fold-left solution with Saxon (EE9.1.7
via Oxygen) I am getting a result of 20 nodes but the correct must be just
3 nodes. BaseX correctly evaluates the XPath expression and produces the
right 3-nodes result.

Xml document:
<t>
  <a/>
  <b/>
  <c/>
</t>

XSLT stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="3.0">
  <xsl:output omit-xml-declaration="yes"/>
  <xsl:template match="/">
    <xsl:sequence select=
      "let $xml := /,
      $nodes := (/*/a, /*/c, /*/b, /*/a, /*/b, /*/a, /*/c, /*/b, /*/a,
/*/b,
      /*/a, /*/c, /*/b, /*/a, /*/b, /*/a, /*/c, /*/b, /*/a, /*/b,
      /*/a, /*/c, /*/b, /*/a, /*/b, /*/a, /*/c, /*/b, /*/a, /*/b,
      /*/a, /*/c, /*/b, /*/a, /*/b, /*/a, /*/c, /*/b, /*/a, /*/b,
      /*/a, /*/c, /*/b, /*/a, /*/b )
      return
        $nodes => fold-left((), function($all, $this) {$all, $this except
$all})"/>
  </xsl:template>
</xsl:stylesheet>

Result produced when run with Saxon-EE (and also PE) 9.9.1.7 via Oxygen:

<a/><c/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/><b/>

Evaluating the below expression with Saxon-EE XQuery9.9.1.7 also produces
the same unexpected result:

let $xml := parse-xml("<t><a/><b/><c/></t>"),
    $nodes := ($xml/*/a, $xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b, $xml/*/a,
$xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b, $xml/*/a, $xml/*/c, $xml/*/b,
$xml/*/a, $xml/*/b, $xml/*/a, $xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b,
$xml/*/a, $xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b, $xml/*/a, $xml/*/c,
$xml/*/b, $xml/*/a, $xml/*/b,$xml/*/a, $xml/*/c, $xml/*/b, $xml/*/a,
$xml/*/b, $xml/*/a, $xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b, $xml/*/a,
$xml/*/c, $xml/*/b, $xml/*/a, $xml/*/b )
  return
    $nodes => fold-left((), function($all, $this) {$all, $this except $all})

Hopefully this is fixed in the next versions of Saxon?

Cheers,
Dimitre


> >
> >
> > On Wed, Dec 29, 2021 at 10:27 AM Martin Honnen martin.honnen@xxxxxx
> > <mailto:martin.honnen@xxxxxx> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx
> > <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>> wrote:
> >
> >  >  I don't have to know one, I just pointed out that the spec doesn't
> >  >   guarantee the order. Thus I don't see why, given the spec, one
> should
> >  >   expect any implementation to preserve the order.
> >
> > I am happy to state that the provided solution produces the correct
> > result on all currently-existing XPath engines :)
>
> As if you had or could verify that. As I said, eXist-db is struggling
> with generate-id based approaches, at least if nodes from different
> document (fragments?) are involved.
> 
>
>

-- 
Cheers,
Dimitre Novatchev
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