Re: Passing distinct subquery solutions to aggregate outer query

Lee,


On Jan 24, 2013, at 0:36, Lee Feigenbaum <lee@thefigtrees.net> wrote:

> Hi Paul,
> 
> Why would the outer query need any graph patterns other than the subquery? You ought to be able to do exactly what you have below without anything in the "what goes here" spot.
> 
That's what I thought at first, but it returns a single solution with no bindings. After studying the spec (SPARQL 1.1 section 12) I see this is probably as specified, because it joins the solution projected from the inner query to the solution from the outer query. The empty outer graph pattern returns a single solution of null bindings (per spec 5.2.1).

Regards,
--Paul

> Lee
> 
> On 1/23/2013 3:56 PM, Paul Tyson wrote:
>> Hi all,
>> 
>> I'm wondering if there is a simple solution to this problem.
>> 
>> I have a rather complicated query, consisting of several union clauses, which by its nature will return duplicates. I need to get a unique solution set so I can group them and sum a couple of fields.
>> 
>> Simply wrapping the union query in a nested SELECT DISTINCT doesn't work,             because the outer query has no graph pattern to match the variables projected from the subquery.
>> 
>> I tried adding a series of BIND statements to simply rename the subquery variables for use by the aggregate outer query, but that didn't work (with jena, at least).
>> 
>> The source dataset is nearly 500M triples. I'm using Jena 2.7.3. The subquery will return anywhere from a few dozen to a few hundred solutions, and by itself runs very quickly.
>> 
>> Here's a skeleton view of the query. Is there something to fill "what goes here" that will pass the subquery results up to the grouping function?
>> 
>> select ?var1 ?var2 (sum(?var3) as ?var3_total)
>> where {
>> { ??? what goes here ??? }
>> {select distinct ?var1 ?var ?var3
>> where { ... complicated union query ... }}
>> }
>> group by ?var1 ?var2
>> 
>> Or any other suggestions on how to tackle this problem?
>> 
>> Thanks,
>> --Paul
>> 
>> 
>