Thanks Eric for raising this issue! The debate about lambda is very complicated and won't be resolved any time soon.
I don't personally know a lot about the > performance of lambdas and welcome arguments on behalf of why lambdas No one probably knows :) - Lambda performance would depend on the JVM implementation. This changes between releases. - Java8+ features forces lambda. For example, ConcurrentHashMap.computeIfAbsent() I believe that we can transform this discussion into specific action items for future commits: For instance, a couple of those specifications would be: - No refactor just for the sake of using Lambda, unless there is a strong technical justification. - Usage of lambda in Unit-tests should be fine. If lambda makes the test more readable, and allows passing method references, then this should make the unit-tests. - We put sample code in the "how-to-contribute" to elaborate "capturing Vs non-capturing" lambda expressions and the implications of each type on the performance. - Without getting into much detail, IMHO, streams should be committed into the code in exceptional cases. The possibility of executing code in parallel makes debugging a nightmare. i.e., Usage of ForEach needs to be justified, what does it bring to the table? On Tue, Apr 27, 2021 at 3:07 PM Eric Badger <ebad...@verizonmedia.com.invalid> wrote: > Hello all, > > I'd like to gauge the community on the usage of lambdas within Hadoop code. > I've been reviewing a lot of patches recently that either add or modify > lambdas and I'm beginning to think that sometimes we, as a community, are > writing lambdas because we can rather than because we should. To me, it > seems that lambdas often decrease the readability of the code, making it > more difficult to understand. I don't personally know a lot about the > performance of lambdas and welcome arguments on behalf of why lambdas > should be used. An additional argument is that lambdas aren't available in > Java 7, and branch-2.10 currently supports Java 7. So any code going back > to branch-2.10 has to be redone upon backporting. Anyway, my main point > here is to encourage us to rethink whether we should be using lambdas in > any given circumstance just because we can. > > Eric > > p.s. I'm also happy to accept this as my personal "old man yells at cloud" > issue if everyone else thinks lambdas are the greatest > -- Best Regards, *Ahmed Hussein, PhD*
