GCP MySQL query logging
It's all documented here and here. 

Relevant part:


  To make your general or slow query logs available, enable the
  corresponding flag and set the log_output flag to FILE. This makes the
  log output available using the Logs Viewer in the Google Cloud
  Platform Console. Note that Stackdriver logging charges apply.
  
  If log_output is set to NONE, you will not be able to access the logs.
  If you set log_output to TABLE, the log output is placed in a table in
  your database. If this table becomes large, it can affect instance
  restart time or cause the instance to lose its SLA coverage; for this
  reason, the TABLE option is not recommended. If needed, you can
  truncate your log tables by using the API. For more information, see
  the instances.truncateLog reference page.