Add validation for derivative arguments

Derivative must be of the form derviative(field, duration) or
derivative(agg(field), duration).

influxql/ast.go

@@ -885,12 +885,48 @@ func (s *SelectStatement) Validate(tr targetRequirement) error {
 		}
 	}
 
+	if err := s.validateDerivative(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s *SelectStatement) validateDerivative() error {
+	if !s.IsNonNestedDerivative() {
+		return nil
+	}
+
 	// If a derivative is requested, it must be the only field in the query. We don't support
 	// multiple fields in combination w/ derivaties yet.
-	if s.IsNonNestedDerivative() && len(s.Fields) != 1 {
+	if len(s.Fields) != 1 {
 		return fmt.Errorf("derivative cannot be used with other fields")
 	}
 
+	aggr := s.FunctionCalls()
+	if len(aggr) != 1 {
+		return fmt.Errorf("derivative cannot be used with other fields")
+	}
+
+	// Derivative requires two arguments
+	derivativeCall := aggr[0]
+	if len(derivativeCall.Args) != 2 {
+		return fmt.Errorf("derivative requires a field and duration argument")
+	}
+
+	// First arg must be a field or aggr over a field e.g. (mean(field))
+	_, callOk := derivativeCall.Args[0].(*Call)
+	_, varOk := derivativeCall.Args[0].(*VarRef)
+
+	if !(callOk || varOk) {
+		return fmt.Errorf("derivative requires a field argument")
+	}
+
+	// Second must be a duration .e.g (1h)
+	if _, ok := derivativeCall.Args[1].(*DurationLiteral); !ok {
+		return fmt.Errorf("derivative requires a duration argument")
+	}
+
 	return nil
 }
 

influxql/functions.go

@@ -39,9 +39,9 @@ func InitializeMapFunc(c *Call) (MapFunc, error) {
 	}
 
 	// Ensure that there is either a single argument or if for percentile, two
-	if c.Name == "percentile" {
+	if c.Name == "percentile" || c.Name == "derivative" {
 		if len(c.Args) != 2 {
-			return nil, fmt.Errorf("expected two arguments for percentile()")
+			return nil, fmt.Errorf("expected two arguments for %s()", c.Name)
 		}
 	} else if len(c.Args) != 1 {
 		return nil, fmt.Errorf("expected one argument for %s()", c.Name)
@@ -86,10 +86,6 @@ func InitializeMapFunc(c *Call) (MapFunc, error) {
 		}
 		return MapEcho, nil
 	case "derivative":
-		if len(c.Args) == 0 {
-			return nil, fmt.Errorf("expected argument in derivative()")
-		}
-
 		// If the arg is another aggregate e.g. derivative(mean(value)), then
 		// use the map func for that nested aggregate
 		if fn, ok := c.Args[0].(*Call); ok {
@@ -136,10 +132,6 @@ func InitializeReduceFunc(c *Call) (ReduceFunc, error) {
 		}
 		return ReducePercentile(lit.Val), nil
 	case "derivative":
-		if len(c.Args) == 0 {
-			return nil, fmt.Errorf("expected argument in derivative()")
-		}
-
 		// If the arg is another aggregate e.g. derivative(mean(value)), then
 		// use the map func for that nested aggregate
 		if fn, ok := c.Args[0].(*Call); ok {

influxql/functions_test.go

@@ -1,6 +1,9 @@
 package influxql
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 import "sort"
 
@@ -117,6 +120,7 @@ func TestInitializeMapFuncDerivative(t *testing.T) {
 		Name: "derivative",
 		Args: []Expr{
 			&VarRef{Val: " field1"},
+			&DurationLiteral{Val: time.Hour},
 		},
 	}
 
@@ -130,6 +134,7 @@ func TestInitializeMapFuncDerivative(t *testing.T) {
 		Name: "derivative",
 		Args: []Expr{
 			&Call{Name: "mean", Args: []Expr{&VarRef{Val: "field1"}}},
+			&DurationLiteral{Val: time.Hour},
 		},
 	}