log_level: integer between 0 and 6 or NULL to leave unchanged.
bigint_as_char: logical: parse int64 as strings instead of double.
date_as_char: logical: parse UTC datetime as strings instead of POSIXct.
Details
Setting log_level to 0 suppresses critical warnings and messages, while 6 is most verbose and displays all debugging information. Possible values for level are:
0: error
1: critical
2: warning
3: message
4: info (default )
5: debug
6: trace
Note that setting it below 2 will suppress important warnings and setting below 1 will suppress critical errors (not recommended). The default is 4.