Re: [xsl] Trouble grouping with for-each-group and sort

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2010-03-17 13:58 -0400, mlcook@xxxxxxxxxx wrote:
> I have a collection of data that I'm trying to sort, but am having
> difficulty with the for-each-group and sort operations.
> ...
> <xsl:for-each-group select="current-group()" group-by="myns:E">
>   <xsl:sort select="current-grouping-key()" data-type="number"/>
>   <xsl:sort select="myns:G/myns:sub3/myns:inner" data-type="number"/>
>   <xsl:call-template name="process-data" >
>     <xsl:with-param name="data-set" select="current-group()"/>
>   </xsl:call-template>
> </xsl:for-each-group>
> ...
> All the other data is grouped and sorted fine, except for the last
> sort on "inner".

Right.

> Any ideas why the last sort doesn't appear to work?

You are missing that your second sort above is sorting the first 
member of each group, it isn't sorting the group as a whole.  You 
have coded the above as if the <xsl:sort> is rearranging the group in 
advance of the called template, and that is not the case.

A group is processed in sorted order ... a group is never sorted as 
is and then used.  In the above I get the impression that you are 
trying to pass the data-set parameter *in sorted order*, and that 
isn't the way XSLT works.  The group is as it is, the processing of 
the groups is ordered by your two sort instructions but the group 
contents themselves are not sorted.

In your process-data template you will have to process them in sorted 
order ... you cannot pass the set of nodes in sorted order.

Sets of nodes in XSLT are in document order.  When you want the 
information ordered, you process them in sorted order.

> Does a data-type of "number" for sorting correctly process numbers
> with decimal points?

Absolutely.

> Am I using the wrong select on the parameter for process-data?

Yes, but there is no select that will pass the set of nodes in sorted 
order.  Sets of nodes are in always in document order.  Sets of nodes 
can be processed in sorted order when you wish.

> Is current-group() at that point not the sorted data that I think it
> should be?

Correct.  I should have read ahead.  Your sort instructions are only 
impacting the processing of the groups, not the members of the 
group.  The members are in document order.

> Is there a limit on nested for-each-group operations?

Not at all.

I hope this helps.

. . . . . . . . . . . Ken

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