When you have a patch that you consider ready for submission, submit it to our code review tool called Gerrit (see Using Gerrit to submit and review patches for details). You’ll see an e-mail go out to the firstname.lastname@example.org list.
As time permits, someone from the core team will review your patch. You will likely need to submit an updated patch with some changes - reply to all the comments in Gerrit at the same time (mark as ‘Done’ those suggestions that you’ve taken without further comment). This process can go back and forth for a while - please don’t be discouraged, you’ll see it happens with all patches!
We maintain a mailing list at email@example.com, which is the right place for Impala development discussions. Questions about using Impala still belong on the Impala user list, which is firstname.lastname@example.org.
This presentation called How to Get Your PostgreSQL Patch Accepted captures a lot of our requirements - particularly the focus on starting small, getting agreement, working on the design first, ensuring proper testing and committing to good comments in the code.