Thanks for your feedback and for making me aware of the complications around Gatherers.
I will also put more thought into how this could work for Gatherers. On Thu, Feb 13, 2025, 23:31 Viktor Klang <viktor.kl...@oracle.com> wrote: > Indeed. I hope I didn't sound discouraging about the possibility to > propagate the stream size information. > > I merely want to emphasize that it may necessitate a slightly broader take > on the problem of propagation of stream-instance metadata, especially in > the face of Gatherers becoming a finalized feature. > > It's great that you started this conversation, Fabian! > > Cheers, > √ > > > *Viktor Klang* > Software Architect, Java Platform Group > Oracle > ------------------------------ > *From:* core-libs-dev <core-libs-dev-r...@openjdk.org> on behalf of Paul > Sandoz <paul.san...@oracle.com> > *Sent:* Thursday, 13 February 2025 20:18 > *To:* Fabian Meumertzheim <fab...@buildbuddy.io> > *Cc:* core-libs-dev <core-libs-dev@openjdk.org> > *Subject:* Re: JDK-8072840: Presizing for Stream Collectors > > Hi Fabian, > > Thanks for sharing and reaching out with the idea before getting too > beholden to it. > > I logged this is quite a while ago. It seemed like a possible good idea at > the time, although I never liked the duplication of suppliers. I have > become less enthusiastic overtime, especially so as Gatherers have been > added. (Gatherer is the underlying primitive we could not find when we were > furiously developing streams and meeting the Java 8 deadline.) My sense is > if we are going to address we need to think more broadly about Gatherers. > And, Viktor being the lead on Gatherers has a good take on where this might > head. > > Paul. > > > On Feb 12, 2025, at 2:09 AM, Fabian Meumertzheim <fab...@buildbuddy.io> > wrote: > > > > As an avid user of Guava's ImmutableCollections, I have been > > interested in ways to close the efficiency gap between the built-in > > `Stream#toList()` and third-party `Collector` implementations such as > > `ImmutableList#toImmutableList()`. I've found the biggest problem to > > be the lack of sizing information in `Collector`s, which led to me to > > draft a solution to JDK-8072840: > > https://github.com/openjdk/jdk/pull/23461 > > > > The benchmark shows pretty significant gains for sized streams that > > mostly reshape data (e.g. slice records or turn a list into a map by > > associating keys), which I've found to be a pretty common use case. > > > > Before I formally send out the PR for review, I would like to gather > > feedback on the design aspects of it (rather than the exact > > implementation). I will thus leave it in draft mode for now, but > > invite anyone to comment on it or on this thread. > > > > Fabian > >
