What is that flag about? If we’re running with version 9+ of Druid, should this flag be set to true?
If buildV9Directly is set to false, Druid will first build a v8 index and then immediately convert it to v9 format before being published.
If set to true, indexing will build a v9 index directly, usually buildv9 is generally faster and also helps in reducing memory pressure on peons.
Refer https://github.com/druid-io/druid/pull/2138 for more details.
For 0.9.x versions of Druid, I would recommended setting it to true.
Great, as faster indexing and reduced memory pressure on peons are two things we very much want.
From reading the pull request, it seems the existence of this flag was just to be safe while the new implementation had a chance to burn in for a while in production. If that has been accomplished, shouldn’t the flag default be true if not removed entirely?
Yes, buildV9 should eventually be the default setting.
Does this flag have an effect on index tasks (batch file-based ingestion)? I noticed that it doesn’t show up in the documentation here: http://druid.io/docs/latest/ingestion/tasks.html
Yes, buildV9Directly affects the batch ingestion as well.