code: func (m *DbMap) TraceOn(prefix string, logger *log.Logger) {
  	m.logger = logger
  	if len(prefix) == 0 {
  		m.logPrefix = prefix
  	} else {
  		m.logPrefix = prefix + " "
  	}
  }
docs: // TraceOn turns on SQL statement logging for this DbMap.  After this is
  // called, all SQL statements will be sent to the logger.  If prefix is
  // a non-empty string, it will be written to the front of all logged
  // strings, which can aid in filtering log lines.
  //
  // Use TraceOn if you want to spy on the SQL statements that modl
  // generates.