Prometheus: Preallocate data for Prometheus backend response parsing (#17490)

pkg/tsdb/prometheus/prometheus.go

@@ -200,7 +200,8 @@ func parseResponse(value model.Value, query *PrometheusQuery) (*tsdb.QueryResult
 	for _, v := range data {
 	for _, v := range data {
 		series := tsdb.TimeSeries{
 		series := tsdb.TimeSeries{
 			Name:   formatLegend(v.Metric, query),
 			Name:   formatLegend(v.Metric, query),
-			Tags: map[string]string{},
+			Tags:   make(map[string]string, len(v.Metric)),
+			Points: make([]tsdb.TimePoint, 0, len(v.Values)),
 		}
 		}
 
 
 		for k, v := range v.Metric {
 		for k, v := range v.Metric {