What you need to remember is that query execution is streaming lazy evaluation. So each time you call hasNext()/next() the minimum amount of work needed to compute the next answer, If any, is done. When you convert the ResultSet into a list you’re doing all that work up front once. When you iterate over the copied Data it is just a static list of the previously computed results. Iterating over a static list has very little overhead computationally, the downside is that it may have a lot of memory overhead if you have a extremely large results. This is a standard space time trade-off and you have to decide what makes sense in your applications context.
Rob On 28/02/2017 16:19, "George News" <[email protected]> wrote: On 28/02/2017 16:59, Andy Seaborne wrote: > > [... snip ...] >> In this sense, one option for including in Jena could be to enable the >> option to create a QueryExecution with transaction included, in order to >> avoid some issues like that. > > That's what ResultSetFormatter.toList or ResultSetFactory.copyResults do. +1 but I don't want to iterate twice over the same list of data. Although at the end I think it would be the easiest way to do it and avoid extra issues ;) > Andy >
