elasticsearch/elasticsearch — pull request #6584 by mikemccand (2014-06-21 17:17:45+00:00)
Title: Core: don't acquire dirtyLock on autoid for create

If we auto-generate the ID and know it cannot already exist then I think we can skip acquiring the dirtyLock for a small perf gain under high concurrency (I see a couple percent gain when _bulk indexing with 10 threads).