Merge pull request #6409 from influxdata/js-4675-derivative-order-by-desc

Allow derivative() function to be used with ORDER BY desc

CHANGELOG.md

@@ -17,6 +17,7 @@
 - [#6444](https://github.com/influxdata/influxdb/pull/6444): Allow setting the config path through an environment variable and default config path.
 - [#3558](https://github.com/influxdata/influxdb/issues/3558): Support field math inside a WHERE clause.
 - [#6429](https://github.com/influxdata/influxdb/issues/6429): Log slow queries if they pass a configurable threshold.
+- [#4675](https://github.com/influxdata/influxdb/issues/4675): Allow derivative() function to be used with ORDER BY desc.
 
 ### Bugfixes
 

influxql/functions.go

@@ -98,11 +98,7 @@ func (r *FloatDerivativeReducer) Emit() []FloatPoint {
 		if !r.ascending {
 			elapsed = -elapsed
 		}
-
-		value := 0.0
-		if elapsed > 0 {
-			value = diff / (float64(elapsed) / float64(r.interval.Duration))
-		}
+		value := diff / (float64(elapsed) / float64(r.interval.Duration))
 
 		// Drop negative values for non-negative derivatives.
 		if r.isNonNegative && diff < 0 {
@@ -149,11 +145,7 @@ func (r *IntegerDerivativeReducer) Emit() []FloatPoint {
 		if !r.ascending {
 			elapsed = -elapsed
 		}
-
-		value := 0.0
-		if elapsed > 0 {
-			value = diff / (float64(elapsed) / float64(r.interval.Duration))
-		}
+		value := diff / (float64(elapsed) / float64(r.interval.Duration))
 
 		// Drop negative values for non-negative derivatives.
 		if r.isNonNegative && diff < 0 {

influxql/select_test.go

@@ -1975,6 +1975,58 @@ func TestSelect_Derivative_Integer(t *testing.T) {
 	}
 }
 
+func TestSelect_Derivative_Desc_Float(t *testing.T) {
+	var ic IteratorCreator
+	ic.CreateIteratorFn = func(opt influxql.IteratorOptions) (influxql.Iterator, error) {
+		return &FloatIterator{Points: []influxql.FloatPoint{
+			{Name: "cpu", Time: 12 * Second, Value: 3},
+			{Name: "cpu", Time: 8 * Second, Value: 19},
+			{Name: "cpu", Time: 4 * Second, Value: 10},
+			{Name: "cpu", Time: 0 * Second, Value: 20},
+		}}, nil
+	}
+
+	// Execute selection.
+	itrs, err := influxql.Select(MustParseSelectStatement(`SELECT derivative(value, 1s) FROM cpu WHERE time >= '1970-01-01T00:00:00Z' AND time < '1970-01-01T00:00:16Z' ORDER BY desc`), &ic, nil)
+	if err != nil {
+		t.Fatal(err)
+	} else if a, err := Iterators(itrs).ReadAll(); err != nil {
+		t.Errorf("unexpected error: %s", err)
+	} else if !deep.Equal(a, [][]influxql.Point{
+		{&influxql.FloatPoint{Name: "cpu", Time: 8 * Second, Value: 4}},
+		{&influxql.FloatPoint{Name: "cpu", Time: 4 * Second, Value: -2.25}},
+		{&influxql.FloatPoint{Name: "cpu", Time: 0 * Second, Value: 2.5}},
+	}) {
+		t.Fatalf("unexpected points: %s", spew.Sdump(a))
+	}
+}
+
+func TestSelect_Derivative_Desc_Integer(t *testing.T) {
+	var ic IteratorCreator
+	ic.CreateIteratorFn = func(opt influxql.IteratorOptions) (influxql.Iterator, error) {
+		return &IntegerIterator{Points: []influxql.IntegerPoint{
+			{Name: "cpu", Time: 12 * Second, Value: 3},
+			{Name: "cpu", Time: 8 * Second, Value: 19},
+			{Name: "cpu", Time: 4 * Second, Value: 10},
+			{Name: "cpu", Time: 0 * Second, Value: 20},
+		}}, nil
+	}
+
+	// Execute selection.
+	itrs, err := influxql.Select(MustParseSelectStatement(`SELECT derivative(value, 1s) FROM cpu WHERE time >= '1970-01-01T00:00:00Z' AND time < '1970-01-01T00:00:16Z' ORDER BY desc`), &ic, nil)
+	if err != nil {
+		t.Fatal(err)
+	} else if a, err := Iterators(itrs).ReadAll(); err != nil {
+		t.Errorf("unexpected error: %s", err)
+	} else if !deep.Equal(a, [][]influxql.Point{
+		{&influxql.FloatPoint{Name: "cpu", Time: 8 * Second, Value: 4}},
+		{&influxql.FloatPoint{Name: "cpu", Time: 4 * Second, Value: -2.25}},
+		{&influxql.FloatPoint{Name: "cpu", Time: 0 * Second, Value: 2.5}},
+	}) {
+		t.Fatalf("unexpected points: %s", spew.Sdump(a))
+	}
+}
+
 func TestSelect_Difference_Float(t *testing.T) {
 	var ic IteratorCreator
 	ic.CreateIteratorFn = func(opt influxql.IteratorOptions) (influxql.Iterator, error) {