I know this is an old post but it comes near the top in google search for ‘davinici resolve no database’.
Fix is to do with user accounts on OSX, I think an OSX update broke postgres.
Mine was the same problem as above, fixed by creating a new user account in OSX called ‘postgres’ gave it a blank password. Opened up the folder in apps ‘PostgreSQL 8.4’ ran ‘Stop Server’ app (had an error doing this until I created new ‘postgres’ account). Now opened ‘Start Server’ in same folder, came back with a server started message. Opened Resolve lite and everything OK.
sugarway.com