On 15/05/13 15:36, Damian Steer wrote:
On 15 May 2013, at 14:10, [email protected] wrote:
Hello,
I am using the following Sparql query against a TDB store:
SELECT *
WHERE {
?pat a nci:Patient .
?pat ec:Has_Id ?patId .
?findingProp rdfs:subPropertyOf ec:Has_Finding .
?pat ?findingProp ?finding .
?finding a ?findingType .
}
When I run this query WITHOUT the last triple (the bolded line), it returns the
correct result within seconds.
Assuming " ?finding a ?findingType" was bold - the email was
quote-prinable - so no markup.
But when I run this query WITH the last triple, the query runs a very long
time. I do not know how long b/c I cancelled it after 1 hour.
I wonder wether the optimiser sees '?finding a ?findingType .' as more ground
than the previous, and thus reorders the query?
Have a look at [1] which explains some of the diagnostic features of TDB.
Getting hold of the query plan would be very useful.
Damian
[1]
<https://jena.apache.org/documentation/tdb/optimizer.html#Investigating_what_is_going_on>
If you could do an "explain" as per Damian's suggestion that would be great
A couple of questions:
1/ Which version is this?
--exaplin may be available if working from the command line
2/ Is there a stats file?
There was a recent fix in this area - if you are using stats.opt, you
may find either adding rules to capture your usage or recalculating. It
may not - ungrounded predicates may be confusing things.
Andy
