On Tue, 24 May 2011 19:16:13 +0200, Kingsley Idehen <kide...@openlinksw.com> wrote:
> On 5/24/11 1:08 PM, Curran Kelleher wrote: >> Greetings, >> >> The problem remains, the following query doesn't execute on the public >> DBPedia endpoint >> <http://dbpedia.org/snorql/?query=select+distinct+%3Fproperty+where+%7B%0D%0A+++++%3Fs+%3Fproperty+%3Fo.%0D%0A%7D+limit+1>, >> even with a limit: >> >> select distinct ?property where { >> ?s ?property ?o. >> } limit 1 >> >> Without 'distinct' it does work: >> >> select ?property where { >> ?s ?property ?o. >> } limit 1 >> >> Why might this be? > > Because Distinct requires more work. > >> Shouldn't the engine be able to work this one out quickly even with >> 'distinct', as it needs to only traverse a single triple to compute >> the result? > > Really? First encounter != distinct :-) >> It seems the engine is doing some unnecessary computation to do with >> 'distinct' and is timing out because of it. > > LIMIT doesn't simply the Distinct computation. It simply limits the > resultset size. > > Kingsley --------------------------------------------------------------------- Don't know much about history, don't know much biology, don't know much about people 'very experienced with DBMS oriented data' but I do know SOMETIHING LIKE this: here again the same with a small correction of my algorithm for general case: a.) read SPARQL query b.) set limit:= {1, ..., MAX} c.) set distinct:= {true, false} d.) set i:=1 e.) compute result item i, if none, set i:=i-1 and break f.) if distinct is true and comparing i'th item with previous result-items results true, goto e.) g.) store i'th item to result-set h.) if i == limit, then break i.) set i:= i+1 j.) GOTO e.) k.) send the result-set to Baran And here i am, thanks. This is a general(!) algorithm with the rationality of a tramp, if LIMIT is 1, for DISTINCT the engine should require nothing, but.. i know, you mean rationality is not elitist enough... Baran ------------------------------------------------------------------------------ vRanger cuts backup time in half-while increasing security. With the market-leading solution for virtual backup and recovery, you get blazing-fast, flexible, and affordable data protection. Download your free trial now. http://p.sf.net/sfu/quest-d2dcopy1 _______________________________________________ Dbpedia-discussion mailing list Dbpedia-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dbpedia-discussion
