What causes "Wrong type %v encountered for func ^" in dgraph-io/dgraph?

Give the predicate a numeric schema type (int/float)

Wrong type %v encountered for func ^

Error message

Wrong type %v encountered for func ^

What it means

applyPow returns this error when an exponentiation (^) operand has DEFAULT type. Power operations require numeric (int/float) typed values; DEFAULT indicates the operand is untyped or its payload is not numeric. Fractional powers of negative bases raise a separate ErrorFractionalPower.

Source

Thrown at query/aggregator.go:352

}

func applyPow(a, b, c *types.Val) error {
	vBase := getValType(a)
	switch vBase {
	case INT:
		c.Value = math.Pow(float64(a.Value.(int64)), float64(b.Value.(int64)))
		c.Tid = types.FloatID

	case FLOAT:
		// Fractional power of -ve numbers should not be returned.
		if a.Value.(float64) < 0 &&
			math.Abs(math.Ceil(b.Value.(float64))-b.Value.(float64)) > 0 {
			return ErrorFractionalPower
		}
		c.Value = math.Pow(a.Value.(float64), b.Value.(float64))

	case DEFAULT:
		return errors.Errorf("Wrong type %v encountered for func ^", a.Tid)
	}
	return nil
}

func applyLog(a, b, c *types.Val) error {
	vBase := getValType(a)
	switch vBase {
	case INT:
		if a.Value.(int64) < 0 || b.Value.(int64) < 0 {
			return ErrorNegativeLog
		} else if b.Value.(int64) == 1 {
			return ErrorDivisionByZero
		}
		c.Value = math.Log(float64(a.Value.(int64))) / math.Log(float64(b.Value.(int64)))
		c.Tid = types.FloatID

	case FLOAT:
		if a.Value.(float64) < 0 || b.Value.(float64) < 0 {

View on GitHub (pinned to 759e242be6)

Solutions

Give the predicate a numeric schema type (int/float)
Validate both operands are numeric before the ^ expression
Re-set or migrate values stored as the wrong type, then rebuild affected indexes

Example fix

// before
math(score ^ 2) // score: DEFAULT
// after
// schema: score: float .
math(score ^ 2)

Defensive patterns

Strategy: validation

Validate before calling

func isPowOperand(v types.Val) bool {
    t := getValType(&v)
    return t == INT || t == FLOAT
}

Type guard

func canPow(a, b types.Val) bool {
    return isPowOperand(a) && isPowOperand(b)
}

Try / catch

if err := applyPow(a, b, c); err != nil {
    switch {
    case strings.Contains(err.Error(), "func ^"):
        return fmt.Errorf("operand type %v not supported for ^; declare numeric schema type", a.Tid)
    case errors.Is(err, ErrorFractionalPower):
        return fmt.Errorf("negative base with fractional exponent")
    }
    return err
}

Prevention

Ensure exponentiated predicates are int/float typed
Avoid ^ on uid or empty values
Check sign/exponent combinations for fractional powers
Validate computed score fields carry a schema type

When it happens

Trigger: math("^", a, b) evaluates where an operand's Tid is DEFAULT — e.g. squaring values of an untyped predicate or an empty/unconverted value reaching the math evaluator.

Common situations: Score computations (e.g. x^2) over predicates missing schema types; exponent variables bound to uid or empty values; data loaded without type conversion.

Related errors

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/4999085a24efe031. Report an issue: GitHub.