execution: enable function acceptance tests again (#523)

* implemented mad_over_time function
* fixed bug with stepinvariant range vectors

Signed-off-by: Michael Hoffmann <[email protected]>
Co-authored-by: Michael Hoffmann <[email protected]>

Author: MichaHoffmann

engine/engine_test.go

@@ -92,7 +92,6 @@ func TestPromqlAcceptance(t *testing.T) {
 		skipTests: []string{
 			"testdata/name_label_dropping.test", // feature unsupported
 			"testdata/limit.test",               // limitk, limit_ratio
-			"testdata/functions.test",           // mad_over_time, predict_linear
 		}, // TODO(sungjin1212): change to test whole cases
 		TBRun: t,
 	}

logicalplan/plan.go

@@ -244,6 +244,12 @@ func replacePrometheusNodes(plan parser.Expr) Node {
 	case *parser.NumberLiteral:
 		return &NumberLiteral{Val: t.Val}
 	case *parser.StepInvariantExpr:
+		// We expect functions to be pushed down into matrix selectors. This means that
+		// parents of matrixselector nodes are always expected to be functions, not step invariant
+		// operators.
+		if m, ok := t.Expr.(*parser.MatrixSelector); ok {
+			return replacePrometheusNodes(m)
+		}
 		return &StepInvariantExpr{Expr: replacePrometheusNodes(t.Expr)}
 	case *parser.MatrixSelector:
 		return &MatrixSelector{

ringbuffer/functions.go

@@ -6,17 +6,16 @@ package ringbuffer
 import (
 	"context"
 	"math"
+	"sort"
 
 	"github.com/efficientgo/core/errors"
-
-	"github.com/prometheus/prometheus/util/annotations"
-
-	"github.com/thanos-io/promql-engine/execution/warnings"
-
 	"github.com/prometheus/prometheus/model/histogram"
+	"github.com/prometheus/prometheus/util/annotations"
+	"gonum.org/v1/gonum/stat"
 
 	"github.com/thanos-io/promql-engine/execution/aggregate"
 	"github.com/thanos-io/promql-engine/execution/parse"
+	"github.com/thanos-io/promql-engine/execution/warnings"
 )
 
 type SamplesBuffer GenericRingBuffer
@@ -82,6 +81,12 @@ var rangeVectorFuncs = map[string]FunctionCall{
 		}
 		return sumOverTime(f.Samples), nil, true, nil
 	},
+	"mad_over_time": func(f FunctionArgs) (float64, *histogram.FloatHistogram, bool, error) {
+		if len(f.Samples) == 0 {
+			return 0., nil, false, nil
+		}
+		return madOverTime(f.Samples), nil, true, nil
+	},
 	"max_over_time": func(f FunctionArgs) (float64, *histogram.FloatHistogram, bool, error) {
 		if len(f.Samples) == 0 {
 			return 0., nil, false, nil
@@ -583,6 +588,23 @@ func histogramRate(ctx context.Context, points []Sample, isCounter bool) (*histo
 	return h.Compact(0), nil
 }
 
+func madOverTime(points []Sample) float64 {
+	values := make([]float64, 0, len(points))
+	for _, f := range points {
+		values = append(values, f.V.F)
+	}
+	sort.Float64s(values)
+
+	median := stat.Quantile(0.5, stat.LinInterp, values, nil)
+
+	for i, f := range points {
+		values[i] = math.Abs(f.V.F - median)
+	}
+	sort.Float64s(values)
+
+	return stat.Quantile(0.5, stat.LinInterp, values, nil)
+}
+
 func maxOverTime(points []Sample) float64 {
 	max := points[0].V.F
 	for _, v := range points {

storage/prometheus/matrix_selector.go

@@ -11,21 +11,18 @@ import (
 	"sync"
 	"time"
 
-	"github.com/prometheus/prometheus/promql/parser/posrange"
-	"github.com/prometheus/prometheus/util/annotations"
-
-	"github.com/thanos-io/promql-engine/execution/warnings"
-
-	"github.com/thanos-io/promql-engine/execution/telemetry"
-
 	"github.com/efficientgo/core/errors"
 	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/value"
+	"github.com/prometheus/prometheus/promql/parser/posrange"
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
+	"github.com/prometheus/prometheus/util/annotations"
 
 	"github.com/thanos-io/promql-engine/execution/model"
 	"github.com/thanos-io/promql-engine/execution/parse"
+	"github.com/thanos-io/promql-engine/execution/telemetry"
+	"github.com/thanos-io/promql-engine/execution/warnings"
 	"github.com/thanos-io/promql-engine/extlabels"
 	"github.com/thanos-io/promql-engine/query"
 	"github.com/thanos-io/promql-engine/ringbuffer"