See below - sorry, realised this message more appropriate for jena-users than jena-dev
Begin forwarded message: > From: Bill Roberts <[email protected]> > Date: 1 April 2011 19:44:20 GMT+01:00 > To: [email protected] > Bcc: Ric Roberts <[email protected]> > Subject: Problems with TDB Optimizer > > I've come across some unexpected (to me!) behaviour of the TDB Optimizer and > wondering if someone could shed any light on it. > > For our database, (around 30 million triples, 350-odd different predicates, > around 50 named graphs, using UnionDefaultGraph - everything is in a named > graph), we've found that including the stats.opt file makes some queries > significantly slower than having no optimizer. > > Some relatively complex queries run quite quickly and probably a bit quicker > with optimization than without. But in other cases, quite simple queries > run a lot slower - maybe 10 or 20 times slower with stats.opt in place than > they do without it. > > Is this known behaviour? > > Here's an example: > > SELECT ?key ?label WHERE { <a-specific-uri> ?p ?key . ?key > <http://www.w3.org/2000/01/rdf-schema#label> ?label } > > This query took around 30 seconds with stats.opt in place, and less than 2 > seconds without it. (Some of that 2 seconds would have been HTTP transfer and > web page rendering time). > > We're currently running TDB 0.8.9 and Joseki 3.4.3 on 64 bit Ubuntu. (Though > I've found similar behaviour on 32-bit Ubuntu with slightly older versions of > TDB and Joseki). > > Thanks! > > Bill
