Need help with Calcite? Try these resources.
The best option is to send email to the developers list dev@calcite.apache.org. All of the historic traffic is available in the archive. To subscribe to the user list, please send email to dev-subscribe@calcite.apache.org.
Please file any issues you encounter or fixes you'd like on the Calcite Jira. We welcome patches!
StackOverflow is a wonderful resource for any developer. Take a look over there to see if someone has answered your question.
One of the advantages of open source software is that you can browse the code. The code is available on github.