code: func (m *DbMap) TraceOn(prefix string, logger GorpLogger) {
  	m.logger = logger
  	if prefix == "" {
  		m.logPrefix = prefix
  	} else {
  		m.logPrefix = fmt.Sprintf("%s ", 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 gorp
  // generates.
  //
  // Note that the base log.Logger type satisfies GorpLogger, but adapters can
  // easily be written for other logging packages (e.g., the golang-sanctioned
  // glog framework).