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It is not a very selective query :) You have zero constants in your query.
Have you tried ALLOW_DUP=T? Does that make a difference?
If that does not help, you need to check the plan and see if hash join is adopted.
For such a query, parallel execution should apply quite well.
The query was not something specific but just an example to illustrate that queries that have several paths can run very slowly.
I'm using with the Jena query QueryOptions.ALLOW_QUERY_INVALID_AND_DUP
How would I check the query plan and whether hash join is adopted?
Also I'm running it in parallel, I'll give this one a try.
The easiest way is to use the SQL monitoring feature that comes with the Enterprise Manager.
It has nice UI and it shows the progress dynamically.
You can also do explain plan from a SQL terminal.
Hope it helps,