The error logging is controlled by the log_error variable (--log-error for a startup script).
If --log-error is not given, the default destination is the console. If --log-error is given without naming a file, the default destination is a file named host_name.err in the data directory . If --log-error is given to name a file, the default destination is that file (with an .err suffix added if the name has no suffix), located under the data directory unless an absolute path name is given to specify a different location.
The log_error_verbosity system variable controls server verbosity for writing error, warning, and note messages to the error log. Permitted log_error_verbosity values are 1 (errors only), 2 (errors ...
