Hello Andy, much better now. Thank you very much :-)
I guess it's OK to rename stats.opt to stats.opt.old instead of moving it out of the directory ? Regards, Michael Brunnbauer On Sat, Aug 04, 2012 at 05:49:41PM +0100, Andy Seaborne wrote: > Hi Michael. > > (Michael has sent me a copy of this database he's using - a bit big too > email even though it's only 157,809,969 triples and 44Gbytes). > > I can recreate this - I'm getting a total of 5006ms for the query set of > 17 queries you're using. > > With a fix, it's 150ms made up of approx 50ms of server-side execution, > 100ms of HTTP networking and results transmission for all 17 queries. > > With the workaround, it's about 170ms. > > Sorry - the fix will not make the next release, which is already built. > Also, my current fix does the right thing for your case but I want > make sure it's not got any concurrency problems. > > > Workaround: > > Remove the "stats.opt" from the database directory and create a file > "fixed.opt" in that directory. An empty "fixed.opt" is fine - it's not > actually read; it's the presence that matters. Caution - you need to > get rid of the stats.opt file as it's used in preference. > > You'll need to see if the change affects other, more complex queries. > dbpedia as a very unusual dataset at the best of times (42K different > unique properties). Depressingly, fixed.opt does a reasonably job of > optimizing. It simply looks for more tightly constrained triple > patterns and mildly avoid rdf:type. > > (The other optimizer option is "none.opt" when BGPs in queries are > executed in the order written. Good for control and experimentation.) > > > Explanation: > > I said: > [[ > But the performance is not to do with stats - this is all single quad > lookup. > ]] > > Not quite true :-) While the statistics themselves don't matter, the > system is reading stats.opt too often. Normally, this isn't too > important because the file is small, heavily cached and fast to parse > (it still shouldn't do it). But the dbpedia stats.opt is big at 2.1 > Mbytes and 42K entries. > > Andy -- ++ Michael Brunnbauer ++ netEstate GmbH ++ Geisenhausener Straße 11a ++ 81379 München ++ Tel +49 89 32 19 77 80 ++ Fax +49 89 32 19 77 89 ++ E-Mail [email protected] ++ http://www.netestate.de/ ++ ++ Sitz: München, HRB Nr.142452 (Handelsregister B München) ++ USt-IdNr. DE221033342 ++ Geschäftsführer: Michael Brunnbauer, Franz Brunnbauer ++ Prokurist: Dipl. Kfm. (Univ.) Markus Hendel
