SSE/Alerting: Support prom instant vector responses (#44865)

* SSE/Alerting: (Draft) Support prom instant vector responses
fixes #35663
* reduce\classic expressions to handle mathexp.Number
* use Notice for warning

Co-authored-by: Yuriy Tseretyan <yuriy.tseretyan@grafana.com>

pkg/expr/mathexp/reduce.go

@@ -100,6 +100,11 @@ func GetReduceFunc(rFunc string) (ReducerFunc, error) {
 	}
 }
 
+// GetSupportedReduceFuncs returns collection of supported function names
+func GetSupportedReduceFuncs() []string {
+	return []string{"sum", "mean", "min", "max", "count", "last"}
+}
+
 // Reduce turns the Series into a Number based on the given reduction function
 // if ReduceMapper is defined it applies it to the provided series and performs reduction of the resulting series.
 // Otherwise, the reduction operation is done against the original series.

pkg/expr/mathexp/testing.go

@@ -0,0 +1,18 @@
+package mathexp
+
+import (
+	"math/rand"
+
+	"github.com/grafana/grafana/pkg/util"
+)
+
+func GenerateNumber(value *float64) Number {
+	size := rand.Intn(5)
+	labels := make(map[string]string, size)
+	for i := 0; i < size; i++ {
+		labels[util.GenerateShortUID()] = util.GenerateShortUID()
+	}
+	result := NewNumber(util.GenerateShortUID(), labels)
+	result.SetValue(value)
+	return result
+}

pkg/expr/mathexp/type_series.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
+
 	"github.com/grafana/grafana/pkg/expr/mathexp/parse"
 )
 
@@ -154,7 +155,21 @@ func (s Series) GetMeta() interface{} {
 }
 
 func (s Series) SetMeta(v interface{}) {
-	s.Frame.SetMeta(&data.FrameMeta{Custom: v})
+	m := s.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		s.Frame.SetMeta(m)
+	}
+	m.Custom = v
+}
+
+func (s Series) AddNotice(notice data.Notice) {
+	m := s.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		s.Frame.SetMeta(m)
+	}
+	m.Notices = append(m.Notices, notice)
 }
 
 // AsDataFrame returns the underlying *data.Frame.

pkg/expr/mathexp/types.go

@@ -2,6 +2,7 @@ package mathexp
 
 import (
 	"github.com/grafana/grafana-plugin-sdk-go/data"
+
 	"github.com/grafana/grafana/pkg/expr/mathexp/parse"
 )
 
@@ -33,6 +34,7 @@ type Value interface {
 	GetMeta() interface{}
 	SetMeta(interface{})
 	AsDataFrame() *data.Frame
+	AddNotice(notice data.Notice)
 }
 
 // Scalar is the type that holds a single number constant.
@@ -55,7 +57,21 @@ func (s Scalar) GetMeta() interface{} {
 }
 
 func (s Scalar) SetMeta(v interface{}) {
-	s.Frame.SetMeta(&data.FrameMeta{Custom: v})
+	m := s.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		s.Frame.SetMeta(m)
+	}
+	m.Custom = v
+}
+
+func (s Scalar) AddNotice(notice data.Notice) {
+	m := s.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		s.Frame.SetMeta(m)
+	}
+	m.Notices = append(m.Notices, notice)
 }
 
 // AsDataFrame returns the underlying *data.Frame.
@@ -121,7 +137,21 @@ func (n Number) GetMeta() interface{} {
 }
 
 func (n Number) SetMeta(v interface{}) {
-	n.Frame.SetMeta(&data.FrameMeta{Custom: v})
+	m := n.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		n.Frame.SetMeta(m)
+	}
+	m.Custom = v
+}
+
+func (n Number) AddNotice(notice data.Notice) {
+	m := n.Frame.Meta
+	if m == nil {
+		m = &data.FrameMeta{}
+		n.Frame.SetMeta(m)
+	}
+	m.Notices = append(m.Notices, notice)
 }
 
 // FloatField is a *float64 or a float64 data.Field with methods to always