Is CREATE INDEX dependent on the session?

Hi,

Would it warrant a clarification in the documentation:
- Whether CREATE INDEX is aborted if the session is disconnected, assuming
it's not in a transaction?
- Ditto for CREATE INDEX CONCURRENTLY?
- Whether CREATE INDEX CONCURRENTLY "returns" immediately or blocks the
session until it's created?

Given how these operations may take substantial time, and have no output
beyond success, this might be a relevant topic.