Adam
Did you try generating the statistics file as well?
Doing that should allow TDB to more intelligently reorder triple pattern
execution within BGPs and hopefully avoid the need to manually adjust queries
Rob
On 15/06/2018, 13:13, "Adam Ladly" <adamla...@hotmail.co.uk> wrote:
Hi Rob,
Just tried re-ordering it as you suggested, and this was exactly the
improvement that I needed. Now getting returns in 0.1 seconds rather than 200+.
Much appreciated,
Adam
________________________________
From: Rob Vesse <rve...@dotnetrdf.org>
Sent: 15 June 2018 12:12
To: users@jena.apache.org
Subject: Re: Long response times on TDB queries
On 15/06/2018, 11:46, "Adam Ladly" <adamla...@hotmail.co.uk> wrote:
22:18:21 INFO exec :: Reorder/generic
?node <http://example.com/idmapping> ?id
?node ?p "http://www.ncbi.nlm.nih.gov/gene/1956";
So it looks like TDB is using a generic execution ordering and for your
data this is clearly sub-optimal, I suspect you have far more triples matching
the first pattern than the second.
Firstly I would try using { } to rewrite your query and explicitly force
the execution order i.e.
PREFIX els: <http://example.com/> SELECT DISTINCT ?id FROM
<urn:x-arq:UnionGraph> WHERE { { ?node ?p
"http://www.ncbi.nlm.nih.gov/gene/1956"; } ?node els:idmapping ?id . }
Although the optimiser might flatten that into a single BGP anyway in which
case you might still have the same problem.
Secondly I would try generating a stats.opt file per the documentation -
http://jena.apache.org/documentation/tdb/optimizer.html#generating-a-statistics-file
Once you have this copy it to stats.opt in your database directory (per the
documentation don't try and generate directly to this location) and then retry
your original query. You should then hopefully see Reorder/stats being used
which if your data is structured as I suspect the statistics should reverse the
order of your triple patterns leading to faster execution
Hope this Helps,
Rob
