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
