add format option for trace (#81)

Co-authored-by: Carl Verge <carlverge@gmail.com>

Author: carl-db

query.go

@@ -23,6 +23,8 @@ const (
 	FormatOptionTable
 	// FormatOptionLogs sets the preferred visualization to logs
 	FormatOptionLogs
+	// FormatOptionsTrace sets the preferred visualization to trace
+	FormatOptionTrace
 )
 
 // Query is the model that represents the query that users submit from the panel / queryeditor.
@@ -158,6 +160,11 @@ func getFrames(rows *sql.Rows, limit int64, converters []sqlutil.Converter, fill
 		return data.Frames{frame}, nil
 	}
 
+	if query.Format == FormatOptionTrace {
+		frame.Meta.PreferredVisualization = data.VisTypeTrace
+		return data.Frames{frame}, nil
+	}
+
 	count, err := frame.RowLen()
 
 	if err != nil {