On Fri, 27 May 2011 01:07:29 +0200, Kingsley Idehen
<kide...@openlinksw.com> wrote:
> On 5/26/11 5:35 PM, baran_H wrote:
>> Without 'distinct' it does work:
>> select ?property where {
>> ?s ?property ?o.
>> } limit 1
>>
>> Why might this be?
>
> So you are asserting that for a given data space hosting N named graphs
> (named collections of triples) :
>
> select ?property where {
> ?s ?property ?o.
> } limit 1
>
>
> and
>
> select distinct ?property where {
> ?s ?property ?o.
> } limit 1
>
> and
>
> select ?property from <namedGraphIRI> where {
> ?s ?property ?o.
> } limit 1
>
> and
>
> select ?property where { graph ?g {
> ?s ?property ?o.
> } } limit 1
>
>
>
> are equivalent.
>
> Again, I say, no re. cost of solution.
>
---------------------------------------------------------
Dear engineer Idehen,
we take our original test-query with distinct:
----------------------------------
select distinct ?property where {
?s ?property ?o.
} limit 1
----------------------------------
The query aims of course only the default graph. We go
to http://dbpedia.org/sparql and see in the page of
query-form 'Query Default Graph http://dbpedia.org',
correct, we send our trivial query, after long waiting
we get 'Transaction timed out'.
Now i as user try to think rationally: First the engine
finds a triple of Default Graph. At this time, considering
DISTINCT, there are no other result items to compare and
because of LIMIT 1 it sends the property of this triple as
result, that's all..
This process is also described in a general algorithm in my
second posting from yesterday.
IF(!) a SPARQL engine makes something completely different
and lets me endless wait for the result,
'Because Distinct requires more work.' as you wrote,
than i assume you would also say: 'Ok, it can be tried to
enhance the engine so that it is smart enough to handle some
trivial cases more effectivly'.
Or, IF(!) you are 'sure' that the extremely slow query
process follows from forceful implementation of SPARQL spec,
THEN SPARQL spec must also be changed,
and now comes the most important statement of my posting:
NOTHING may violate rationality in this way...
What can i write more?
Thanks, Baran.
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