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From Andy Seaborne <>
Subject Re: [jira] Commented: (JENA-40) Query that runs more or less forever
Date Thu, 03 Feb 2011 21:47:48 GMT

Could we have things like slow queries on the user list to start with, 
please?  If there's an underlying issues, then move to JIRA but until 
there is an addressable issue, JIRA does not work for me for discussing 
query design.  It's quite possible in SPARQL to write very expensive 

SELECT * { ?s ?p ?o . ?x ?y ?z }

and ARQ/TDB's design means such queries will execute and finish 
eventually.  But its N^2 results on a database of N.  And N tends to be 
a decently large number. In fact, it wouldn't even use very much memory 
for that query, because of internal streaming.


On 03/02/11 15:52, Benson Margulies (JIRA) wrote:
>      [
> Benson Margulies commented on JENA-40:
> --------------------------------------
> Changing the OPTIONAL's to UNION and adding the necessary constraint to both of them
also makes it run in reasonable time/
>> Query that runs more or less forever
>> ------------------------------------
>>                  Key: JENA-40
>>                  URL:
>>              Project: Jena
>>           Issue Type: Bug
>>           Components: TDB
>>             Reporter: Benson Margulies
>>          Attachments: r.rq, yk.txt
>> Using the data set you have from me, the following query, which looks very much like
a series of other queries that run quite rapidly, shows no sign of finishing.

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