Sorry for yet another mail. Is there some document from which I can understand how ORDER BY and LIMIT clause are evaluated by Jena. I read the documentation here: http://jena.apache.org/documentation/query/arq-query-eval.html but I am not able to understand the solution from it.
On Tue, Mar 10, 2015 at 11:24 AM, Rose Beck <[email protected]> wrote: > Hi, > > I saw the following issue posted on Jena website (which has been > recently resolved): > Avoid a total sort for ORDER BY + LIMIT queries > (https://issues.apache.org/jira/browse/JENA-89). > > I am very interested in understanding as to how does Jena-ARQ avoids > total sort for ORDER BY + LIMIT queries. In the post it is mentioned > that Jena-ARQ uses priority queue for avoiding a final sort, however > it is also mentioned that "ARQ's algebra package contains already a > OpTopN [3] operator. The OpExecutor [4] will need to use a new > QueryIterTopN instead of QueryIterSort + QueryIterSlice." It is not > clear now does the priority queue benefit from OpTopN operator and > QueryIterTopN as the links [3] and [4] mentioned on the website does > not work, so I am not able to understand their operation and as to how > do they help in avoiding a total sort. > > Can someone please explain how does Jena-ARQ execute the queries > containing ORDER BY + LIMIT clause. > > With Warm Regards, > Rose -- With Warm Regards, Rose
