Re: [Qexo-general] problems aggregating with sum()

[Per Bothner]

Kevin Y. Kim (Lists) wrote:
> If I have an XML file, input.xml, that looks like this:
> <record id="1">
>     <key>A</key>
>     <value>1</value>
> </record>
> <record id="2">
>     <key>B</key>
>     <value>2</value>
> </record>
...

That is not a well-formed XML file.  At least, it is not a legal
"XML document", which can have only a single top-level element.

> I want the output to look like this:
> <record>
>     <key>A</key>
>     <value>5</value>
> </record>
> <record>
>     <key>B</key>
>     <value>7</value>
> </record>
> <record>
>     <key>C</key>
>     <value>3</value>
> </record>

Likewise not valid XML.  It could be valid in the XQuery data model,
if you view it as a sequence of elements.

> When I try this xquery with Qexo, I get an exception:
> record><key>A</key><valueInvalid parameter, was: null
> java.lang.ClassCastException
>         at gnu.kawa.functions.Arithmetic.asNumeric(Arithmetic.java:169)
>         at gnu.kawa.functions.AddOp.apply2(AddOp.java:76)
>         at gnu.kawa.functions.AddOp.applyN(AddOp.java:118)
>         at gnu.kawa.functions.AddOp.applyN(AddOp.java:133)
>         at gnu.mapping.ProcedureN.apply2(ProcedureN.java:39)
>         at gnu.xquery.util.Reduce.combine(Reduce.java:26)
>         at gnu.xquery.util.Reduce.apply1(Reduce.java:42)
>         at atInteractiveLevel$2.run(test.xq:13)

> As far as I can tell, the problem is the SUM() function.

Correct.  The "test.xq:13" refers to line 13, specifically the sum.

> Just on a lark, I changed the SUM() to COUNT() - and it does
> report the correct number of items in the sequence.

The problem is that $recs/value/text() evaluates to a sequence of
text nodes, and Qexo doesn't know how to convert each text node
to a number - only to a string.  This has to do with complicated
XQuery typing rules - which Qexo doesn't implement correctly yet.
As a work-around try:
  sum(for $none in $recs/value/text() return number($node))
--
        --Per Bothner
address@hidden   http://per.bothner.com/