Hi Jonathan, > On 20 Dec 2017, at 14:47, Jonathan Bluett-Duncan <jbluettdun...@gmail.com> > wrote: > > Hi Paul, > > It seems that some clever Googler managed to find a workaround for aggressive > `flatMap` operations in the form of a so-called `MoreStreams.flatten` > operation, implemented in a side project called google/mug.
Thanks. MoreStreams.flatten “lowers” a stream of streams to a spliterator of spliterators which in turn is input as a new stream source, enabling a cancellation check + tryAdvance for any following short-circuit or terminal ops. I have a solution in the works for flatMap based on sorted operation (which has to buffer all elements, sort ‘em, then push ‘em all downstream). Paul. > I'm sharing the javadoc > <https://google.github.io/mug/apidocs/com/google/mu/util/stream/MoreStreams.html#flatten-java.util.stream.Stream-> > and GitHub project homepage <https://github.com/google/mug> with you and the > rest of the mailing list in the hope that they prove to be useful. > > Cheers, > Jonathan > > On 20 December 2017 at 21:28, Paul Sandoz <paul.san...@oracle.com > <mailto:paul.san...@oracle.com>> wrote: > Hi, > > Please review this fix for a bug in the stream takeWhile operation: > > > http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/ > > <http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/> > > <http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/ > > <http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/>> > > The flatMap operation is currently aggressive and does not detect if a > downstream operation may or has cancelled processing, and will push all of > it’s elements downstream. Short-circuiting operations should be guarded > against such behaviour but unfortunately takeWhile was not guarded. > > — > > Separately i plan to figure out a way to ensure flatMap operations become > less aggressive if there are short-circuiting downstream operations. This may > increase efficiency and also allow support for flat map results that are > infinite. > > Paul. >
