Sebastian,
What indexes are in use? It seems to me that only default indexes are
created, but patterns with unspecified graph need, of course, two
additional indexes. If the speed of the first query is suitable and you
do not want to create additional indexes for some reason, consider
select * where {
graph ?commonGraph {
?r a nfo:FileDataObject .
?r nie:isPartOf ?f . }
OPTIONAL { ?g <http://www.strigi.org/fields#indexGraphFor> ?r . } .
FILTER(!BOUND(?g)) .
}
if the modification is acceptable.
Best Regards,
Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com
On Tue, 2009-10-27 at 12:44 +0100, Sebastian Trüg wrote:
> Just out of curiosity:
> why is there such a big difference in performance between the following 2
> query variants (second one much slower than the first)
>
> select * where {
> ?r a nfo:FileDataObject .
> OPTIONAL { ?g <http://www.strigi.org/fields#indexGraphFor> ?r . } .
> FILTER(!BOUND(?g)) .
> }
>
>
> select * where {
> ?r a nfo:FileDataObject .
> ?r nie:isPartOf ?f .
> OPTIONAL { ?g <http://www.strigi.org/fields#indexGraphFor> ?r . } .
> FILTER(!BOUND(?g)) .
> }
>
> The only difference is one more graph pattern.
>
> This is Virtuoso 5.0.12 with
>
> [Parameters]
> LiteMode=1
> ServerPort=1120
> DisableTcpSocket=1
> PrefixResultNames=0
> ServerThreads=100
> CheckpointInterval=10
> NumberOfBuffers=10000
> MaxDirtyBuffers=50
> SchedulerInterval=5
> FreeTextBatchSize=1000
>
> Cheers,
> Sebastian Trüg
>
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