Hi everybody.
I use a Virtuoso instance installed on ubuntu (Virtuoso version:
07.20.3214, Build: Oct 14 2015), in order to execute sparql queries. My
queries are quite complex and make heavy use of the "OPTIONAL" pattern.
While I have used the same queries on another virtuoso endpoint (not
controlled by me) I cannot seem to use them on mine. I keep getting the
message
"Virtuoso 42000 Error The estimated execution time 0 (sec) exceeds the
limit of 18000 (sec)."
As you see, I have changed the timeout parameters in the virtuoso.ini
file and put an irrational value (18000 seconds!!!). Still, it seems
that the engine would refuse to execute my query.
My questions are:
1. Is the value "0" mentioned as execution time a special value or is it
just a bug? Is it logical to assume that the virtuoso estimates that the
query would require infinite time to execute?
2. Are there any other configurations that I could do in order to
improve situation?
3. Is there anything that I should keep in mind when I use the
"OPTIONAL" sparql query pattern? I mean, is there a documented (even
informally) way of improving the performance of queries using OPTIONAL
clauses?
Kind regards,
Pantelis Natsiavas
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