app/vmselect/promql: remove metric name after applying clamp_min and clamp_max functions in order to be consistent with Prometheus

This improves VictoriaMetrics score at https://promlabs.com/promql-compliance-test-results-victoriametrics/

app/vmselect/promql/exec_test.go

@@ -645,7 +645,6 @@ func TestExecSuccess(t *testing.T) {
 			Values:     []float64{1000, 1200, 1400, 1400, 1400, 1400},
 			Timestamps: timestampsExpected,
 		}
-		r.MetricName.MetricGroup = []byte("foobar")
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
@@ -657,7 +656,6 @@ func TestExecSuccess(t *testing.T) {
 			Values:     []float64{1000, 1200, 1400, 1400, 1400, 1400},
 			Timestamps: timestampsExpected,
 		}
-		r.MetricName.MetricGroup = []byte("foobar")
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})

app/vmselect/promql/transform.go

@@ -17,11 +17,6 @@ import (
 	"github.com/valyala/histogram"
 )
 
-var transformFuncsKeepMetricGroup = map[string]bool{
-	"clamp_max": true,
-	"clamp_min": true,
-}
-
 var transformFuncs = map[string]transformFunc{
 	// Standard promql funcs
 	// See funcs accepting instant-vector on https://prometheus.io/docs/prometheus/latest/querying/functions/ .
@@ -130,12 +125,8 @@ func newTransformFuncOneArg(tf func(v float64) float64) transformFunc {
 }
 
 func doTransformValues(arg []*timeseries, tf func(values []float64), fe *metricsql.FuncExpr) ([]*timeseries, error) {
-	name := strings.ToLower(fe.Name)
-	keepMetricGroup := transformFuncsKeepMetricGroup[name]
 	for _, ts := range arg {
-		if !keepMetricGroup {
 		ts.MetricName.ResetMetricGroup()
-		}
 		tf(ts.Values)
 	}
 	return arg, nil