Grouping By Time / Round xs:time to just the hour?

[Oliver Hallam]

  On 08/07/2010 18:21, Andrew Serff wrote:
> So two questions:
> 1) How do I add the leading 0 to the output of hours-from-dateTime?
> 2) Is there an easier way of doing this?
>
> Thanks for the help!
> Andrew
>

1)  The only way i can think of is

if ($hour<  10) then concat('0', $hour) else $hour

2) You could just group your input by the result of hour-from-dateTime:

<metrics>
{
   let $m := collection('metricsCollection.xml')//metrics/metric[action = 'QUERY']
   let $timestamps := for $ts in $m/timestamp return xs:dateTime($ts)
   for $hour in distinct-values(for $timestamp in $today return hour-from-dateTime($timestamp))
   let $hours-timestamps := $timestamps[hour-from-dateTime($timestamp) = $hour]
   return
     <res><h>{$hour}</h><metrics>{count($hours-timestamps)}</metrics></res>
}
</metrics>

Of course if you actually want your date in the result then you are 
still stuck with converting your hour back to a time.

Oliver