Hi William,

thanks for providing me with the sample documents. Unfortunately, I
cannot give you a general answer on how to avoid the slowdown of your
query, as appears to be the result of numerous single optimizations
(flwor rewritings, static bindings, functions inlinings, etc.), which
are performed in the compilation step. You might check out the Query
Info in the GUI, or use -V on command line, to get some more insight
into the query compilation process.

After all, I have added your use case to our internal bug tracker, and
I might have a closer look at this phenomena after the next official
release.

Hope this helps,
Christian



On Tue, Jan 11, 2011 at 3:34 PM, William Sandri wrote:

Hello,
we are experiencing a weird performance issue in function calling.
In many xqueries we use, we found that calling functions slows down the
execution, sometimes it even hangs "forever".
I tried to drill down to the problem and I think I isolated an odd behavior.
Before presenting the example code, let me summarize a little bit:
inside a for-loop we call a thousand times a function passing some
parameters.
I declared 3 functions, 2 of which take 1 parameter and the last one takes 2
parameters.
For simplicity's sake the parameter "objectId" is never used, but that
doesn't affect the experiment.
When I call any of the 1-parameter functions, execution takes less than 2
seconds, but when I call the 2-parameter function it runs endlessly.
It seems that the combination of those two parameters is the point of
performance issue.
I hope you can illuminate me.
Regards
William

Here it is an example:

declare namespace xbpr = "http://www.bpeng.com/";

declare variable $amlDocName as xs:string :="aml";
declare variable $cxnDefsDocName as xs:string :="cxnDefsDocName";

declare function xbpr:testFast1($objectId as xs:string?){
let $docName := $cxnDefsDocName
let $conn_typeof_target :=
doc($docName)/CxnDefs/CxnDef[@type="RdfsType"]/@target
return $conn_typeof_target
};

declare function xbpr:testFast2($docName as xs:string?){
let $conn_typeof_target :=
doc($docName)/CxnDefs/CxnDef[@type="RdfsType"]/@target
return $conn_typeof_target
};

declare function xbpr:testSlow($docName as xs:string?, $objectId as
xs:string?){
let $conn_typeof_target :=
doc($docName)/CxnDefs/CxnDef[@type="RdfsType"]/@target
return $conn_typeof_target
};

let $instances := doc($amlDocName)/AML/Group//ObjDef
for $instance in $instances
    let $objectId := $instance/@ObjDef.ID
    let $v := xbpr:testFast1($objectId)
    let $v := xbpr:testFast2($cxnDefsDocName)
    let $v := xbpr:testSlow($cxnDefsDocName, $objectId)
  return $v


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