I would personally use another element or even split the date and time into
two fields. Then you would use a range index on the date field of the type
date. Of course, you can also just store the date part as an attribute of
the current element and work off of an element-attribute-index and wrk on
the same solutions.
to get your results (pseudocode)
for $res in (for $date in cts:element-values(xs:QName("yourdatefieldhere"),
(set the frequency order options here)
return
<res><date>{$date}</date><count>{cts:frequencies($date)}</count></date>)
order by $res/count
return $res
the result from element-values is from an index and is already a list of
distinct-values.
Regards,
David
On 10 April 2014 22:50, Jakob Fix <[email protected]> wrote:
> Hello,
>
> How would one go about this one: I'm storing dateTime values for each
> document.
> I want to retrieve, efficiently, all unique dates (irrespective of the
> time part) and the number of items with that date.
>
> The naive implementation (because it takes about 1.5 seconds for not much
> data):
>
> let $c := collection("item")
> return
> for $d in distinct-values($c !
> xs:date(xs:dateTime(.//normalized-dateTime/text())))
> order by $d descending
> return concat($d, " - ",
> count($c//item[xs:date(xs:dateTime(.//normalized-dateTime)) = $d]))
>
> The profiler tells me that it's spending about 85% of the time in the
> predicate in the last line, so an index would probably speed up the lookups.
>
> I created an element range index for the normalized-dateTime element, of
> type dateTime. What I was hoping to be a bit less naive, turns out to be
> not feasible:
>
> for $d in distinct-values(collection("item")/item !
> xs:date(xs:dateTime(./normalized-dateTime/text())))
> order by $d descending
> return concat($d, " - ",
> count(
> cts:search(/item,
> cts:and-query((
> cts:collection-query("item")
> ,
> cts:element-range-query(xs:QName("normalized-dateTime"), "=", $d)
> ))
> )
> )
> )
>
> Now it complains that there is no element range index of type date for the
> normalized-dateTime element, which is correct...
>
> Would the recommendation be to add another element, normalized-date, that
> contained only the date part and work with that, or is there possibly
> another, even simpler solution?
>
> cheers,
> Jakob.
>
>
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