[xquery-talk] Optimizations

Fri Oct 3 16:14:27 PDT 2008

I think you ran this with Saxon-B. Saxon-SA does more powerful
optimizations, and produces

<query>
  <globalVariables>
    <declareVariable name="level">
      <literal value="3" type="xs:integer"/>
    </declareVariable>
  </globalVariables>
  <declareFunction name="local:debug" arity="1" tailRecursive="false">
    <literal value="()"/>
  </declareFunction>
  <body>
    <let variable="dosmthg" as="element(oki,
{http://www.w3.org/2001/XMLSchema}anyType)">
      <be>
        <directElement name="oki" validation="preserve">
          <valueOf>
            <literal value="test trace" type="xs:string"/>
          </valueOf>
        </directElement>
      </be>
      <return>
        <sequence>
          <literal value="()"/>
          <variableReference name="dosmthg"/>
        </sequence>
      </return>
    </let>
  </body>
</query>

One of the optimizations that's done in Saxon-SA but not in Saxon-B is
function inlining.

Michael Kay
http://www.saxonica.com/

  _____  

From: talk-bounces at x-query.com [mailto:talk-bounces at x-query.com] On Behalf
Of Rémi Dewitte
Sent: 03 October 2008 14:17
To: talk at x-query.com
Subject: [xquery-talk] Optimizations

Hi,

I have made a little experiment after reading Michael (Kay) blog posts about
optimizations and recent James Fuller article.

I have a question quite specific to saxon still interesting in general.

Why in the following example even the function call is not skipped ?

XQuery is ::

declare variable $level := 3;

declare function local:debug($what){
  if($level >=4) then
    <debug>{$what}</debug>
  else ()
};

let $dosmthg := <oki>test trace</oki>

return
(local:debug($dosmthg),$dosmthg)

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