On 19/09/12 18:51, Yuhan Zhang wrote:
Hi all,
I kept categories of videos as triples in a tdb in the format of (?video_id
?category ?score)
I'd like to find videos with similar categories given one video id.
select ?video_2 COUNT(*)
where {
<http://onescreen.com/video/2901760> ?c ?score_1 .
?video_2 ?c ?score_2 .
}
group by ?video_2
limit 100
Illegal syntax?
However, this query with a group by was really slow and never completed.
There are about 21M triples in the same tdb.
The response was pretty fast when querying without a group by.
How could I make thie query faster? Is SPARQL the right tool for this?
You data modelling looks somewhat unusual. A join across the predicate
(?c) is likely to cause an explosion in possibilities.
The LIMIT 100 applies after grouping - and the groups are likely huge.
What is
select (count(distinct ?p) AS ?pCount) { ?s ?p ?o }
select distinct ?p { ?s ?p ?o } limit 10
Andy
Thank you.
Yuhan
