The MySQL error log in MySQL 5.7

The MySQL error log has received some attention in MySQL 5.7, with a new setting called log_error_verbosity.
There are three possible values, as documented in the manual:

Verbosity Value Message Types Logged
1 Errors only
2 Errors and warnings
3 Errors, warnings, and notes (default)

As Giuseppe has written about previously, writing notes or “informational events” can create debugging problems because they reduce the signal to noise ratio. There is now an easy way to reduce the logging to be only warnings and errors!