Barry Coughlan created JENA-502:
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Summary: VALUES keyword in subquery ignored in some cases.
Key: JENA-502
URL: https://issues.apache.org/jira/browse/JENA-502
Project: Apache Jena
Issue Type: Bug
Components: Fuseki
Affects Versions: Fuseki 0.2.7, Fuseki 0.2.8
Environment: Ubuntu 13.04 x64
OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1ubuntu0.13.04.2)
Reporter: Barry Coughlan
Given the following data set in the graph "http://test.com":
{code:title=data.ttl}
@prefix : <http://example.com/>
:s1 :type :thing .
:s1 :p1 :o1 .
:s2 :type :thing .
:s2 :p1 :o1, :o2 .
:s3 :type :thing .
:s3 :p1 :o2 .
{code}
{code}s-put http://localhost:3030/ds/data http://test.com data.ttl{code}
Suppose, as part of a subquery, we want to find all subjects that have (:p1
:o1):
{code}
PREFIX : <http://example.com/>
SELECT *
WHERE {
SELECT DISTINCT ?s WHERE {
GRAPH <http://test.com> {
?s :p1 ?obj .
VALUES ?obj { :o1 }
}
}
}
{code}
This returns the expected result (?s={:s1, :s2}). However when the GRAPH
statement is outside the subquery:
{code}
PREFIX : <http://example.com/>
SELECT *
WHERE {
GRAPH <http://test.com> {
SELECT DISTINCT ?s WHERE {
?s :p1 ?obj .
VALUES ?obj { :o1 }
}
}
}
{code}
this returns ?s={:p1, :p2, :p3} - the VALUES block is ignored by the query, and
removing the VALUES block gives the same result.
Going back to the first query, let's try to select all triples with subjects
restricted by the subquery:
{code}
PREFIX : <http://example.com/>
SELECT ?s ?p ?o
WHERE {
{SELECT DISTINCT ?s WHERE {
GRAPH <http://test.com> {
?s :p1 ?obj .
VALUES ?obj { :o1 }
}
}}
GRAPH <http://test.com> { ?s ?p ?o }
}
{code}
I expected the subquery to restrict ?s to {:s1, :s2} and the triple at the
bottom to select all triples with that subject. This behaviour works as
expected in OpenRDF Sesame. However, once again the VALUES keyword is ignored
and the following output is observed:
{code}
s p o
:s1 :type :thing
:s1 :p1 :o1
:s2 :type :thing
:s2 :p1 :o1
:s2 :p1 :o2
:s3 :type :thing
:s3 :p1 :o2
{code}
I have tried this with other triples in the subquery, and the behaviour is as
expected. It seems to be variables restricted with the VALUES keyword that
misbehave.
Another curiousity I found while trying to find a workaround. If I add the
VALUES variable to the SELECT, changing the line {code}{SELECT DISTINCT ?s
WHERE {{code} to {code}{SELECT DISTINCT ?s ?obj WHERE {{code} then I get the
expected result of only :s1 and :s2 being selected. However, this is not
suitable as a workaround because if there is more than one value in the VALUES
block, there will be duplicate values for ?s.
Sorry for the long bug report, I'm not exactly sure of what the problem is so
thought I would give as much detail as possible. I discovered this first on
0.2.7 but ran most of these tests on the 0.2.8 build from
jena-fuseki-0.2.8-20130804.075208-67-distribution.tar.gz.
Regards,
Barry
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