Diferent case, but again hanging makes no sense to user, whatever are
the technical reasons.
VALUES ?sct_code { "298314008" }
?c skosxl:prefLabel [ lsu:code ?sct_code ]
returns one row immediately, but
VALUES ?sct_code { "298314008" }
?c skosxl:prefLabel [ lsu:code ?sct_code ]; skos:inScheme
lsu:SNOMEDCT_US
hangs forever
skos:inScheme lsu:SNOMEDCT_US;
On 18/10/2022 9.08, Lorenz Buehmann wrote:
Hi,
comments inline
On 17.10.22 14:35, Mikael Pesonen wrote:
This works as a separate query, but not in a the middle, since ?s
gets new values instead of binding to previous ?s.
{ select ?t where {
?s a ?t .
} limit 10}
?t skos:prefLabel ?l
In the middle of what? Subqueries will be evaluated first - if you
really want labels for classes, you should use a DISTINCT in the
subquery such that the intermediate result is small, there shouldn't
be that many classes, but many instances with the same class, thus,
the join would be more expensive than necessary.
On 17/10/2022 14.56, Mikael Pesonen wrote:
?s a ?t .
?t skos:prefLabel ?l
returns 3 million triples. Maybe it's related to this?
I don't see how this should be related to your initial query where ?s
was bound, which in my opinion should be an easy join. Is it possible
for you to share the dataset somehow? Also, what you can do is to
compute statistics for the TDB database with tdbstats tool [1] from
commandline and put it into the TDB folder. But even without the query
plan should take the first triple pattern, use the spo index as s and
p are bound, then pass the bindings of ?o to the evaluation of the
second triple pattern
[1]
https://jena.apache.org/documentation/tdb/optimizer.html#generating-a-statistics-file
On 21/09/2022 9.15, Lorenz Buehmann wrote:
Weird, only 10M triples and each triple pattern returns only 1
binding, thus, the size is tiny - honestly I can't think of
anything except for open connections, but as you mentioned, running
the queries with only one triple pattern works as expected, so that
too many open connections shouldn't be an issue most likely.
Can you reproduce this behavior with newer Jena versions like 4.6.1?
Or can you reproduce this on different servers as well?
Is it also stuck of your run the query directly after you restart
Fuseki?
On 19.09.22 13:49, Mikael Pesonen wrote:
On 15/09/2022 17.48, Lorenz Buehmann wrote:
Forgot:
- size of result for each triple pattern? Might affect if hash
join can be used.
It's one row for each.
- your hardware?
Normal server with 16gigs mem.
- is it just the first query after starting Fuseki? Connections
have been closed? Note, there was also a bug in a recent Jena
version, but only with TDB and too many open connections. It has
been resolved with release 4.6.1.
Jena has been running quite a while.
Might not be related, but I'm mentioning all things here
nevertheless.
On 15.09.22 11:16, Mikael Pesonen wrote:
This returns one row fast, say :C1
SELECT *
FROM <https://a.b.c>
WHERE {
<https://x.y.z> a ?t .
#?t skos:prefLabel ?l
}
and this too:
SELECT *
FROM <https://a.b.c>
WHERE {
#<https://x.y.z> a ?t .
:C1 skos:prefLabel ?l
}
But this always hangs until timeout
SELECT *
FROM <https://a.b.c>
WHERE {
<https://x.y.z> a ?t .
?t skos:prefLabel ?l
}
What am I missing here? I'm using Fuseki web GUI. Thanks!
--
Lingsoft - 30 years of Leading Language Management
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Mikael Pesonen
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e-mail: mikael.peso...@lingsoft.fi
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