elasticsearch/elasticsearch — pull request #5785 by kimchy (2014-04-12 10:12:20+00:00)
Title: Don't lookup version for auto generated id and create

When a create document is executed, and its an auto generated id (based on UUID), we know that the document will not exists in the index, so there is no need to try and lookup the version from the index.
For many cases, like logging, where ids are auto generated, this can improve the indexing performance, specifically for lightweight documents where analysis is not a big part of the execution.